One of the first structures that most visitors to the Acropolis see, the Propylaea is a headliner of tours of Athens’ ancient sites. It was planned around the natural entrance to the plateau where the Acropolis is set, and the stairway that once led up to its central gate was built into the plateau’s rock slope. Dating from the 4th century BC, the Propylaea was designed to align with the Parthenon, and is the earliest example of urban planning that includes buildings positioned in relation to one another. The best way to visit is with a guide for insights to help interpret the ruins and understand their historic and architectural significance.