Tetrapylon

'four fronts', also used in English) is a rectangular form of monument with arched passages in two directions, at right angles, generally built on a crossroads.

The normal Roman type is square, with the four faces usually very similar; these are found "from Spain to Syria", with a probable example in England.

Although at an important crossroad in the city, the Arch of Septimius Severus at Leptis Magna has three steps up from the road level, suggesting that it was not passed through by wheeled traffic.

A tetrakionion (Koinē Greek: τετρακιόνιον), plural tetrakionia, is a type of tetrapylon in which the central crossing is not roofed, and the four corner-markers exist as four separate structures, now unconnected, but perhaps originally supporting coverings in perishable materials such as wood and fabric.

The South Tetrapylon at Jerash seems to have had this form, as well as structures in Anjar, Lebanon, Ephesus, and other cities, all in the Eastern Roman Empire, apart from a tomb in Pompeii that is much smaller than the examples on streets.

[4] The relatively small example at Aphrodisias, Turkey is rather different, with the two groups of columns on each side of the roadway joined by open pediments over arches, while none of the structure crosses the road itself.