The Cryptoporticus, Market and Tetrapylon of Bosra

Beneath the north portico of Bosra’s main east-west street runs a vaulted gallery 108 metres long: the cryptoporticus, a covered underground passage. At its east end is the entrance to a Roman market building, or macellum; at its west end is the round square of a tetrapylon built in the 4th century. The three belong together. They are layers of one piece of town, and the stretch of the main street walk most easily missed. Whether the cryptoporticus is open to visitors today could not be confirmed with a dated source; the description below follows the Ifpo guide to Bosra.

Where it is

On the north side of the main street, between the entrance of the market building and the tetrapylon square. The tetrapylon stood at the crossing of the main street with the north-south street that runs down to the al-Jahir spring.

What the underground gallery is like

The cryptoporticus is a straight, vaulted gallery: 108 metres long and 5 metres wide, with an apse at each end. The walls are basalt blocks, rendered with pink mortar on the north side. The vault is Roman concrete mixed with volcanic slag. In the south wall, 34 light openings that widen inwards open onto the street beneath the portico. There are niches in the walls and three doorways on the north side.

Suleiman al-Muqdad discovered and cleared the gallery in the 1960s and 1970s, and new soundings were made between 1998 and 2001. The first phase dates to the end of the 2nd or the start of the 3rd century. At that time steep stairs led down into the gallery from the square above. In the 4th century gentle ramps, easier for moving goods, replaced the stairs, and the floor was raised by about 60 centimetres.

The Roman market

The east end of the cryptoporticus now lies under a modern house. On the street, four columns on pedestals formed the entrance portico of the market; according to Ifpo, three are still in place. Parts of a building with a symmetrical plan were found under houses that are still lived in: a round or octagonal centre with semicircular exedrae at the corners. The plan is compared with the Roman markets of Jerash and Apamea.

The tetrapylon and the round square

A tetrapylon is a monumental crossroads structure standing on four bases. Only the bases are left. At Bosra there are four square pedestals, each a little over 5 metres a side, and each once carried four columns. The rough-grooved cores of the capitals survive; they were most likely cut this way to take gilded bronze plating.

The square was laid out at the end of the 3rd or the start of the 4th century. At that point the west end of the cryptoporticus was shortened by 10 metres and closed with a wall and a door, and its west apse was partly demolished. The paving of the round square differs from that of the street: small square stones set at 45 degrees. The two streets divide the square into four quarters. Each quarter had a façade with Ionic pilasters and shop doors, fronted by a pavement linking the porticoes of the two streets. The closest parallel is the south tetrapylon of Jerash; the tetrapylon on the main street of Palmyra is of the same type. The square and its surroundings were abandoned in the 6th or 7th century.

What an ancient text says

The Expositio totius mundi et gentium, a 4th-century description of the world, mentions Bosra this way: “Bostra, where people admire the public work called the tetrapylon.”

What not to miss

Look down. The most distinctive trace the sources describe is the paving of the tetrapylon square. Where the street enters the square the stones change direction, and small square stones are laid at 45 degrees. Even with the pedestals ruined, the edge of the square can be traced from this paving.

Current state

The ancient city of Bosra is visited; an Al-Watan article dated 3 September 2026 describes it as a tourist site. No dated source could be found showing whether the cryptoporticus, the market or the tetrapylon square are standing and open to visitors today. Ask first. If you plan to go down into the gallery, check locally, and do not enter an enclosed, dark underground structure alone.