The builders of the Giza pyramids feasted on food from a massive catering-type operation, the remains of what scientists have discovered at a workers' town near the pyramids.

여기서 what이 틀린거라는데 이해가 안가서요, discover의 목적어 아니에요?

왜 틀린건지, 뭘로 바꿔야 맞는지 설명부탁드려요.