Greek architecture, emerging in the 9th century BC, is noted for its simplicity, harmony, and proportion, exemplified by the Parthenon. Roman architecture, more ornate and grandiose, focused on public buildings and innovations like concrete, with the Colosseum as a prime example.

Roman architecture historically came after Greek architecture; thus, most of it was inspired by the Greeks. Greek architecture was focused on looking good on the outside, but Roman architecture improved since it had visual appeal both inside and outside. Romans experimented with concrete, domes, and other new building forms for better looks.

Greek and Roman architecture share many similarities because the Romans borrowed largely from the three architectural orders that the Ancient Greeks established. The Romans were innovative in their own right, though, and developed arches and vaults that set them apart from the Greeks.

Greek architecture stretches from c. 900 B.C.E. to the first century C.E., with the earliest extant stone architecture dating to the seventh century B.C.E. Greek architecture influenced Roman architecture and architects in profound ways, such that Roman Imperial architecture adopts and incorporates many Greek elements into its own practice.