Could anyone comment feasibility on the 'Cowboy Bebop'-style para-terraforming postulated on Mars by creating a small non-domed, livable section inside of a large crater, where the crater walls are high enough to 'contain' enough of the greenhouse gases being produced by the settlements? [0] Would we be better off just building huge domes, or digging underground?

[0]https://i1.wp.com/www.inetres.com/gp/anime/bebop/02/bebop_02...