Remnants

During millennia of space exploration, human travellers found remnants and ruins of ancient alien civilizations. It was "Knock, knock, who's there?" but there was no answer...

Source: tatoeba (1468174)

Had any stranger passed by he would have wept also; for the whole flower garden was wrecked; naught remained but trampled mould and remnants of plants, with here and there some solitary flower that had escaped being crushed to pieces, and which with its colours yet gay and bright looked still beautiful, though fallen.

Source: tatoeba (6213369)

Pulsars are dense remnants of dead stars that regularly emit beams of radio waves, which is why some call them "cosmic lighthouses."

Source: tatoeba (6479021)

Soon the disenfranchised, downtrodden laymen started a full out uprising, seeking to tear out the remnants of their oppression.

Source: tatoeba (6907372)