The propylaea are, in architecture, a monumental entrance with columns to a building or closed area.[1]​.

In Ancient Greece, the singular word própylon or propylaeo (in ancient Greek, plural, προπύλαια, composed of the prefix προ pro and the noun πύλαιον pylaion — Προπύλαιον = 'in front of the door') designated a simple vestibule located in front of the entrance to a shrine "Shrine (building)"), palace or city.

In plural, the propylaea (Προπύλαια) are monumental entrances or porticos with a much more complex structure, such as in Eleusis, Corinth, Epidaurus or Athens. They frequently had a wall or also called a façade with columns.

In the Hellenic sphere, the oldest preserved monumental propylaeum is the entrance to the temenos of the sanctuary of Aphaia in Aegina, a two-sided structure in antis, with two Doric columns on each face. Both in this case and later in Athens, this construction also served to hide the steep slope of the access road, made up of monumental stairs. It was carried out at the same time as the reconstruction of the sacred precinct, dated around 500 BC. C. The remains of a previous monumental entrance, evidenced by excavations, have been dated to around 570 BC. c.

The oldest known non-detached propylaea is the one found in the palace area of ​​Pasargadae, an ancient Achaemenid capital.[2]​.

In front of the Palace of Darius") in Susa, on the mound of the royal city, there is a covered passage called the propylaea.[3]​.

In Baalbek you can still see the propylaea from the time of Caracalla, erected in the 17th century.