Caves
Natural Caves have been found near the volcano Arsia Mons on Mars.
The caves are a possible location to establish a human settlement. They could be re-constructed to become big habitats. The caves would provide shelter and plenty of space for housing. They could, perhaps, also be a source for water and rare minerals.
Nadine Barlow said: "Caves on Mars could be good places for long-term ice accumulation and that would make them ideal locations to look for life on Mars as well as valuable reservoirs for water to support future human exploration of the planet."
What a joy to find somneoe else who thinks this way.