A Greek or Roman concert hall with tiered seating, built on a circular plan, and covered with a roof. It was probably used for concerts and speeches. The earliest is that constructed by Pericles at Eleusis (Athens) in 435 BC. Roman examples exist at Pompeii, Lyons, and Pula. An important example is that of Agrippia in the Agora at Athens; it differed from later odeums in its square shape and pointed roof.