As if one huge gateway from antiquity isn't enough, the Pergamon museum also houses the Ishtar Gate from Babylon. This gate, done in a decorated blue ceramic tiles, fills an entire room and behind it is a small section (only a few hundred feet in length) of the Babylonian processional way which led to it. For more views of the Ishtar gate and Pergamon Altar, look here.

Ishtar Gate
Ishtar Gate