Orbiter is a free-to-play space flight simulator developed by a single man Martin Schweiger since 2000 (the last major update was on 2016) and using realistic physics. Originally it's a very bare-bones program, but has a lot of fan-made addons which make the simulator much more enjoyable. One of those addons is Orcus Patera - a fictional human base/spaceport located in Orcus Patera depression on Mars; the addon is developed by Well and DanSteph.
Here are some images of the base modified in New Rome addon (which uses more recent Mars HRSC high-res texture pack and places the base in Valles Marineris):