Planet of Ruins

I'm not entirely sure of all the specifics Dyson Logos had in mind when he posted about Rocket & Ruins, but here's what I imagined:

• Earth in an early star-faring stage
• Solar system is kind of boring
• Mundane colonization beginning around nearby stars
• Explorers find a planet completely covered in ruins of an alien city.

The Terrans haven't met any intelligent aliens yet. The planet of ruins is the first evidence of an alien race. Thus, the Planet of Ruins is the most interesting thing in this setting so far. And it's covered in ruins, with no wilderness and no exposed ocean. The only life is vermin, some with very weird features. The Terrans are here to find out more about the alien civilization and exploit what they find.
There are alien artifact, although mostly not near the surface. The good stuff is down below.

Unfortunately, there may also be experimental life forms in stasis, or weird alien breeding machines. Fiddling with the wrong machine may result in the release of "goblins", or "balrogs". The style of the campaign can thus change over time, based on what the explorers do.