Two lions tearing a bull apart; the left half of the sculpture is a modern reconstruction. The lion/bull motif is fairly common in ancient Greek art; I've always wondered if it's supposed to symbolize the ascendancy of the Mycenaean culture (whose symbol was the lion) over the earlier Minoan civilization (whose symbol was the bull). The Minoans collapsed around 1500 BC or so, and the Mycenaeans rose to real prominence throughout the Aegean within 50 years of that collapse. I think that's what the lion/bull scene is supposed to commemorate.