Surviving Mars: Below and Beyond is an expansion for the management strategy game set in a sci-fi setting. It adds the ability to build underground bases, explore caves, and extract exotic materials. Now you can build your colony in caves and lava tubes beneath the planet's surface. You can set up a research base in existing buildings or in special underground structures. Be careful with collapses, as they can destroy everything.
The expansion requires the original version of Surviving Mars.