Philadelphion

The Philadelphion was a public square located in Constantinople.

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.

According to the 8th-century Parastaseis syntomoi chronikai, the site of the later Philadelphion was originally known as the Proteichisma ("fore-wall"), and the site of a gate in the city wall built by Emperor Carus (r. 283–284).Raymond Janin suggested that this Proteichisma was an outer defensive wall protecting the wall erected by Septimius Severus (r. 193–211) during his rebuilding of Byzantium, possibly indicating that the city had already expanded beyond the Severan wall. The Parastaseis record the presence of statues of Constantine the Great (r. 306–337), his mother Helena, and his sons, seated on thrones, around a large four-sided porphyry column, topped by a gilded cross and marked with the sign of a sponge at the base, as well as statues of Julian the Apostate and his wife, whom the Parastaseis erroneously records as Anastasia. Perhaps this was a statue of Constantine's sister Anastasia. According to the Parastaseis, the column was erected by Constantine to commemorate his having a heavenly vision of the cross at the site; modern scholarship however considers the monument complex to be of later date, commemorating the finding of the True Cross by Helena. The Patria of Constantinople furthermore records that statues of two sons of Constantine seated on thrones stood opposite from the column. These statues apparently survived until the early 15th century, when they were popularly known as the "True Judges".

...
Wikipedia