Vultaum Colony

A thorough scan of … has revealed a vast, artificially-constructed network of tunnels beneath the …'s surface. Most of the tunnels have collapsed, and the crew of the … believe they represent only a small portion of what was once a much larger subterranean Vultaum colony. The main underground caverns were intentionally collapsed, crushing the Vultaum cities and their inhabitants under several million tons of rock.

The command below will trigger the "Vultaum Colony" event in Stellaris:

When this event fires, you can choose between the following option:

• Remarkable.
  • Start special project: Tunnel Network