Lost Civilizations: themed area with an architecture that resembles the ancient ruins of extinct civilizations.

Dust is a substance that was leftover from an extremely powerful, ancient, extinct civilization only known as the Endless.

Finding a new nebula or star cluster could be just as enjoyable as discovering a new bit of pottery from an extinct civilization.

The rooms contained treasure and artifacts of an extinct civilization.

Some were underwater completely in the bog that was once a crater and before that was part of an extinct civilization.

Bornstellar is seeking Precursor artifacts, relics from an extinct but technologically superior civilisation.

The latter is said to go back in time for 100 million years and encompass long extinct ancient civilizations.

There were vanished traces of extinct civilizations here and there, some of them puzzlingly fragmentary.

Apart for their community, the planet is empty (aside from artefacts of an extinct civilisation).

The remains of an extinct civilization!