What are some realistic locations for a secure location high above the ground?

Question

I am trying to work out whether it is realistic to have a collection of locations throughout a near future Earth, that are high above the ground (eg. sky, trees, buildings) but secure and either not very visible/obvious or very difficult to get to. These could be either in an urban or completely natural setting, but as well as the above, there's the consideration that supplies and maintenance will still be required. So the added challenge is how to still allow outside workers and supplies in without compromising the security of the location?

Some examples I have thought of:

• building atop a mountain where the severe conditions sheild the visiblity and make it difficult to get to
• skycraper with dedicated (otherwise inaccessible) floors and blacked out windows
• I have considered some kind of large aircraft, but I think that would be too expensive and difficult compared to other building based solutions.

Some additional details without getting too much into plot:

• Think something along the lines of secret rebel hideouts
• Budget doesn't matter as much since the occupant/rebels of some locations may have more wealth than others eg. wealthy urban rebels may use a skyscraper hideout, while humble rural rebels may use a mountain fort

Answer 1

This detail makes all the difference:

... Secret rebel hideouts ...

While there are many valid answers for securing something up high, a secret rebel hideout has extra considerations that matter. For one, secrecy is just as important as security. An airship or mountain top fortress might be hard to access, but they stand out against their backgrounds such that surveillance is bound to detect them. As for the hideout part, radio towers will be way too small.

This makes skyscrapers the ideal location

Because a skyscraper is already host to thousands of visitors a day, and has a massive logistics need, you can drive trucks full of supplies and rebels in and out of the place all day long and no one will see anything unusual happening there. This means no amount of aerial reconnaissance will reveal your location.

While one other answer suggests using unofficial space like mechanical floors, such places will be prone to inspection by outside agencies and will have no legal stop-gap in place to keep law-enforcement or fire inspectors out. Using the building's official space would be even better.

Because it is common for skyscrapers to host a variety of data sensitive civilian firms (Banking institutions, IT companies, medical records firms, law offices, etc), high security in parts of the building is 100% to be expected. All you need to do is buy up a bunch of office space and establish a small front office that looks legitimate. As long as your front should legitimately be following an escalated security standard like PCI, CMMC, HIPPA, etc. then no one will really question why you have such strict visitor policies, plus it gives you rights to limit certain kinds of access to law enforcement.

For example, let's say a cop shows up and he has a warrant to search your "medical archives company", because of HIPPA, his warrant will generally be very limited in scope. In most cases, your office staff can prevent the officer from doing a physical search under the grounds that a cop could not reasonably search for the thing of interest without going through records which are protected under HIPPA and are not part of his investigation; so, it would be common practice for your archive staff to fetch things of interest (like specific medical records) for the cops rather than granting physical access.

Or another example might be if a fire inspector drops by unannounced. If you were hiding in the mechanical floors, you would be discovered. However, if as a high security firm, you can tell him you need time to secure your sensitive information and schedule him to come back later after you've had time to hide all of your illegal, I mean "sensitive" materials.

As a last line of defense, a skyscraper has the added advantage of being positioned right above the heads of thousands of innocent civilians. This means that if your location is discovered, they can't just call in an airstrike without incurring massive political fallout. If they want to assault your position, they have to go in by foot without the advantages of air or artillery support. This gives your rebels a fighting chance to hold the position long enough to destroy records, await reinforcements, or if they are fanatical enough, to detonate any self-destruct devices there might be.

Answer 2

Airships

For once, these are a good answer. You've said that resupply is required, but that the main consideration is altitude. For that, passive lift is difficult to beat. They benefit from economies of scale, too. Airships are handy because you can move them, so you can change to different areas of interest without having to incur your construction costs again.

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Edit after OP Clarification

Airships are too visible for this purpose, even in remote areas. Thank you for that clarification.

Answer 3

Water Towers

Nobody goes knocking on the front door of a water tower.

Construction:

Getting your own water tower (without it being obvious that it doesn't actually hold water) is probably the hardest part. There are a few ways to do this, with the one I'd recommend being:

1. Find a good location, between two fairly large towns (so there's justification for having a fairly large water tower)
2. Convince both of them, through bribing some employees, that the water tower belongs to the other town/city
3. If necessary, have someone who works for each town who can fake anything necessary to keep the secret

Design:

Some water towers have pretty wide columns/towers to hold them up; if you go for a design with one central one holding it up, you can fit an elevator and some rooms into it.

The main part is of course the giant "tank" on top. You can't have windows, but with a sufficiently large design you could probably fit a considerable number of rooms and people inside.

You also get the advantage of fairly good fortification; even if your water tower is revealed as a fake, it'll be pretty sturdily constructed anyway due to the huge weight of water is supposedly holds.

Answer 4

Hide in plain sight

Sometimes the best way to hide is to go where there are so many people that you won't be noticed. Hiding in a skyscraper is a great idea. Every large building has a lot of space dedicated to maintenance and operations. I used to work in a building that had a whole wing of offices that I couldn't access with my keycard. I never tried to get in or asked what was there. My coworkers never expressed any curiosity about it either. You could hide a lot of people in the upper floors of a building, even if the building is actively being used by other workers. And resupply would be as easy as unlocking the front door or tossing some rope down to the ground (you can buy 80 meters of strong rope for around $400).

EDIT: As Darrel Hoffman points out in the comments, you could easily remain hidden by hiding in one of a highrise's mechanical floors. The linked article shows just how much space different skyscrapers devote to these non-occupied floors.

Answer 5

Radio towers.

source

They would be more impressive if they were not so ubiquitous. And old. The American landscape is dotted with towers, in town and in the country side. Radio towers are really tall and also built to last. If the top of a building is not ideal for your purpose (available buildings not tall enough or too accessible) then siting your operation on a radio tower might work. Radio towers often host cell phone antennas in their lower reaches.

You will be limited by space and weight. You cannot put a mobile home on the top of a radio tower. You cannot host a dance party... hmm. Maybe there is a way to host a dance party....

Answer 6

Alpine Bunkers

They can be super high up and hidden in plain sight, just like these buildings in Switzerland. It might be interesting to check out the concept of the National Redoubt in general.

Answer 7

You can have different ways of going away from the surface of Earth, but you said that being at the top of a mountain is also possible if that means that the access is difficult and there is poor visibility.

So, we are searching for means of being high above the plains, and if there is a way up to your place, that it must have low visibility or be difficult to access or to traverse. These are your options:

-Airships, as Anon already said, you can get passive lift from lighter-than-air gasses. Also the bigger you make them you will have more space to put gas in and get a greater load up in the air. They can be pretty manouverable too. Now for the specifics: You have two possible gasses to use: Hellium (He, non reactive, very scarce on Earth) or Hydrogen (H, reacts violently if you put it with Oxygen and blow a spark: see the Hindenburg disaster, however, it's a lot easier to contain, it has a greater lift capacity and it is very easy to produce through the electrolysis of water). There are more Lifting gasses if you are interested in continuing to research this option. Airships will also need fuel and oil to run the motors; periodic maintenance checks to the superstructure, the motors, the air sacks, the water ballast, etc; a way to obtain lifting gas, as it will slowly dissipate through the cover...

-The top of mountains + castles. You already commented about it. The fact is that you can try that, but if the objective is to run from zombies or the like, I recommend to make the scenery in Europe, where you might find a great density of castles, forts, batteries, walled cities, and other types of fortifications. You will usually find them at the top of mountains. In Spain and Portugal (Iberian Peninsula) you may have a special case. As they waged a 'war' for over 700 years with an enemy to their south and it has a very irregular orography, you will find a nice evolution of castles from north to south. If you are looking exclusively for difficulty of access you will be able to find some fine examples like the Segovia Castle, the Alhambra, the Palace of Sintra or some superfortifications like the fortified complex of Elvas. However, for forts more contemporanean than 1850 I sugest not to look in Spain.

Or make the scenery on the coast of America (North and South). While it may sound contradictory to mix coast and top of mountain, you will not be dissapointed. Here's an example of what you can find:

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-Second to last, the top of buildings. It is a plausible aproach to the problem, however there will be a lot of problems with getting supplies to the top unless you are able to use a lot of man-powered cranes and long and resistent enough rope. You could use the lifters' holes to put the cranes at the top. Probably there won't be any electricity so that means that basic things like water pumping and active air ventilation won't work.

-For the last one, it's not exactly an airship, but if you already have all the materials and you have a complex enough chain of crafting to make each component, you could make a space station and live there, and using hydroponics to get food. Actually, this last one would be the most safe one, because you would be far from the ground, with difficult access (because you need a rocket to get there) and supplies and maintenance will always be required.

Answer 8

Oil Rigs

There's the classic example of SeaLand that has been used over the years by various groups as an off-grid escape, but a full size commercial Oil platform way out in the middle of the ocean would be an idea. You can get supplies in/out by sea and air, it would be relatively easy to protect, and depending on how far out to sea it is, would be difficult for attackers to get to unless they're very well equipped.

You'd see anyone coming from miles away, and a point defence system would keep things relatively protected. A lower cost solution to protection could be the large fire suppression hoses which would be enough to knock down an incoming chopper or flatten any marauders trying to scale the sides.

Answer 9

I would say The Moon. It's not that hard to get to. We've been there many decades ago, but not just anyone can go easily. You would be able to see any large enough structure with telescopes but small enough structures in the craters would be hard or impossible to see. Or if you really want to hide, then just make the base on the 40% or so of the moon that isn't visible from Earth. Obviously resupply would be an issue if the moon base wasn't self sufficient. But it's not hard to maintain security in this case, since I would think it's relatively easy to detect and validate any incoming spacecraft.

Another, less realistic, option would be, some sort of additive to clouds that make them able to support weight or some foundation material that was less dense than clouds so it could float and be suspended in the cloud. The cloud would hide the structure to everything but planes and such.

Answer 10

How about nuclear airplanes?

No development project has seen completion, but such an airplane would fly for years without landing, more with a minimum level of handwaving (a molten salt reactor could potentially be refueled in flight, for example).

Supplies and personnel can be rotated with smaller, conventional planes who can hook themselves under the mother plane, a precision manoeuvre but well inside the means of current technology.

Unlike air ships the mother plane can reach very high altitudes to the order of 20km, making it virtually invisible, and it could possibly be designed for radar stealth. It would probably have to get lower to meet with the supply deliveries, though.