You may have crash-landed on this planet, but it seems you weren't the first to settle here. Abandoned Ruins adds ruins to world generation for you to explore and build into your own base, but be careful... Just because the ruins are long since abandoned, their defences might not be as dormant.
Mods introducing new content into the game.
As far as I'm aware, both The Ruins Mod and the Adventure Ruins fork are no longer in active development. Abandoned Ruins is a from scratch rewrite taking inspiration from Gangsir / Bilka's mod, but doesn't reuse any of the code or ruins.