This is the monumental tomb of Lyciarch Marcus Aurelius Archepolis in the North Necropolis. It is dated to the second half of the 3rd century AD. There used to be a vault covering the tomb (collapsed) and three sarcophagi inside, one, the Sidamara sarcophagus, is now in the Antalya museum.
A Lyciarch was one of the principal officials of the Lycian League: the Lyciarch and the archiereus.