The Philadelphion was a public square located in Constantinople (today's Istanbul). After passing the Forum of Theodosius, the Mese Odos (the main road of Constantinople) branched into two directions. One led to the quarter known today as Yedikule, via the Aksaray and Cerrahpaşa quarters. The other passed through the quarters of Şehzadebaşı and Fatih until reaching the quarter of Edirnekapı (formerly the Gate of Charisius). The space where the road forked was thought to be the physical centre, or mesomphalos, of the city.
Statues of the Tetrarchs (two Augusti and two Caesari) in the act of embracing themselves were to be placed on the shafts of two adjacent columns, along with other statues. This was one of the squares where imperial processional ceremonies took place. The statues could represent Emperors Diocletian and Maximian, and their respective Caesars Galerius and Constantius Chlorus. The patria identifies them as sons of Constantine the Great.
The square existed intact until the 8th century. The statues of the Tetrarchs were plundered during the Fourth Crusade in 1204 and brought to Venice (a missing fragment was found near the Bodrum Mosque). 
Media related to Philadelphion at Wikimedia Commons
- Striker (1981), p. 29
- Striker, Cecil L. (1981). The Myrelaion (Bodrum Camii) in Istanbul. Princeton NJ: Princeton University Press.