Mars: First, a Pascal Dome
The idea is simple...
1. Send a robot probe or two out to find a BIG ice rock, either in singles or a cluster, boost the ice to Mars.
2. Crash it into the planet making a nice new deep crater that is, coincidentally, got that big chunk of ice water in the middle of it.
3. Cover the crater with a dome or even a air tight fabric cover before the volatiles are lost.
This reservoir of (mostly) water then supports an initial colonial development cluster; A town. Housing, agriculture, life support and manufacturing is built around the contained crater.
Over time, possibly over decades...
1. The pressure and air quality under the dome is adjusted to something that is human breathable.
2. The temperature can be adjusted within the dome to something comfortable.
3. At some point lights can be added sufficient to grow orchards.
But at first, the purpose is simply resources.
The end result, however, is a Town Green. There is now a park in the center of a development where people can go for a picnic or just to have a little bit of space instead of walls. I think that humans can do well in tight spaces, in extremely small spaces. But not without relief, not without somewhere to go that has some space. Several ice rock craters in a cluster is a series of parks in a city.
Hey, sounds great for the first bunch of ice rocks dropped, right? What about later, when there are other settlements to drop rocks on top of? Aiming shouldn't be that hard, if we can send robot landers that land where we want them to land. And new colonies can purchase bonds in case of accidents.
Mars has water, so what's the point? Yes, Mars does have water, but it's going to be hard enough to get, along with all the other gasses and whatnot to fuel life support and hydroponics, that the boost at the beginning is a good idea.