It has been suggested that lava tubes at Hadriacus Mons could provide a location for a human habitat that would screen out harmful radiation.
My idea for a colony is that it was initially built inside the lava tube (which I gather is huge - 190m wide, 160m tall (100m below surface). This could hold say a 50-story structure of some kind. Once in place, you could extend structures through the surface with radiation protection so you could have windows and a view outside.
Space isn't a problem, but I'm thinking materials are. Assume this is in the future and we have advanced ships and a presence on Mars for many decades - beyond exploration and into settling.
Question: What's the best method to build a city colony structure in the lava tube?
Would it make the most sense to build a "skyscraper" inside with access to the surface? Or would there be some better way to build in this huge open space? Alternately you could begin tunneling in to the rock itself within the tube and build inside the Mars rock itself.
Apparently you might be able to make "mooncrete" (https://en.wikipedia.org/wiki/Lunarcrete) - could you make a sort of "marscrete?"
NOTE: Think long term, big city, permanent settlement - we are past the exploration stage.
EDIT: People are still thinking of the exploration/astronaut stage -- think more about this as a full fledged functioning colony 100 years later. As I said in my note - big city. We are beyond worrying about potatoes for food and oxygen. We have the technology to reliably put oxygen safely in the whole structure. We can ship food and materials in from Earth or other colonies. That's the background. Now we want the best structure with that in mind inside the lava tube.