Far to the north, in a slushy and storm-torn wasteland, a city stands. Massive pillars jut hundreds of feet into the sky from their anchors deep beneath the rising and falling tides below the city. Spanning these pillars is a vast, multi-layered network of webs. Buildings of spider silk hang from these webs, swaying gently (or perhaps violently) in the wind, and on any given day massive trained spiders crawl the webs, repairing broken cords and making new buildings.
What kind of changes are necessary to make spiders large enough to maintain this city? Apparently the role of oxygen in making massive creatures is more complicated than I thought, and it's not enough to just say "it's a high-oxygen world."
- The spiders must be large enough so that webs they make can feasibly hold up at least one layer of a city. A strand of spider silk the size of your little finger might actually be overkill for building purposes. I'm imagining these spiders as being roughly four to six feet in length, but I could be wrong.
- The pillars of the city are arranged in whatever shape is most stable - hexagons, I believe. A single "level" is composed of the web spun within a single hexagon. There are many hexagons throughout the city, and many layers within the hexagons. Multi-story buildings tend to be built on their sides.
- These spiders could be natural or created. You have access to as much genetic technology as you desire.
- Sticky silk would be undesirable in most places, so any genetic modifications that reduced the amount of sticky silk produced would be desirable.
- We already have a reasonable idea as to what they would eat, so I imagine their handlers would regularly purchase goats and sheep and whatnot, although toddlers may occasionally go missing.
- I would prefer to stick as close to our natural Earth as humanly possible.
I'm looking primarily for world changes that make giant spiders feasible, such as atmospheric conditions or ecosystem requirements. A good answer would either describe the kind of world these creatures could have evolved naturally in (and maybe some possible ideas for what these changes might mean for other creatures? maybe that's another question entirely) or explain what kind of genetic alterations might make this happen. Possibly a mix of the two - maybe this world has some atmospheric differences that make it very easy to genetically modify existing creatures to fit this description.