The Ancient Forum, the administrative centre of ancient Thessaloniki, occupied an area about two hectares in the heart of the city. Its construction began at the end of the 2nd century A.D. on the site of an older forum dating from early Imperial times.

The complex was arranged around a rectangular paved square. The Forum concentrated all public services and at the same time it also served inhabitants’ social lives. In the double portico of the southern wing were shops which could be reached through a narrow, marble-paved, commercial street. Remarkable are the square, the baths, the Odeion, the Mint and the document Archive. The Forum was entered through the magnificent Colonnade of the Enchanted Idols- the Incantadas, as it was also known (those statues were transferred to Louvre museum by Emmanuel Miller in 1864). There were stoas on three sides, each of which consisted of a double row of columns and provided direct access to a surrounding zone of public buildings. The southern stoa stood on a vaulted substructure (cryptoporticus) - a double arcade which lay partly underground, making use of the natural slope of the land. To the south, along the whole of the cryptoporticus, lay a row of shops fronting the ancient shopping street which ran along the north side of present-day Philippou St. Off this street lay minor entrances to the square, while the latter opened north, to the present-day Olympou St. In the middle of the east wing, on the site of an earlier council - chamber, a building for public performances was erected, which, on the basis of the inscription and the statues of Muses found there, must have functioned as an odeon.

At presen the recovered part of the Forum is the result of the excavations, which took place in 1966 for the construction of the Courthouse at this place of the city - hence the name 'the Courthouse square' (Plateia Dikastirion). However, the courthouse has never been built at that place. The Forum, having the shape of the Greek letter í, was set around a rectangular paved square having a length of 146 meters and a width of 97 meters, which was free only from the north side. What has been brought into light through the excavations, proved to be of major significance as far as the topography and the history of the city are concerned. On the northwestern side , a large rectangular area with traces of marbled pavings was recovered and on the eastern side an Odeion with bricked tiers and a stage were recovered, too. On the southern side part of an underground stoa, parts of a colonnade, mosaic floors, marble stairs, part of a stone paved street, sewers, sewer pipes etc. were brought into light. A lot of silver coins and stone marble sculptures were founded. An important paleochristian wall painting, which depicted two men praying with a cross between them, was found on a wall of the stoa. Above them the Christ was seated on a throne. This wall painting testifies that the Roman Forum might have been used as a place where the Christians of the town used to gather in the late roman times.

Today the southeastern part of the Square, which is about 100 meters long and 65 meters wide, is visible. However, the complex expands to the northwest beyond the limits of the excavation site, under the foundations of the adjacent blocks of flats. The Square Along the three sides' except the northern one, which was free ' there were double colonnaded stoas of Corinthian style and mosaic floors. In the background there was a section of rooms. Out of the two hundred columns which existed, the only one which is rescued with its original Corinthian capital is the one which today stands at a random position in the square and belonged to the inner side of the colonnade. It had fallen in a sewer of the eastern stoa and it was restored in 1966 by the archaeologist F. Petsas.

The entrance to the open space of the Forum was from the north side, where median street (messi odos), one of the main streets of the town in the early roman times, crossed. The residents of Thessaloniki used to gather at this place in order to attend lectures of their fellow townsmen and local courts open to the public or to discuss political and philosophical issues. Marble posts with notices about important events of the city or invitations to shows were set up here. Furthermore, there were honorary statues of significant persons of the town erected in the Square. Along the three sides of the Square, double colonnaded stoas existed and in the background a section of rooms, which housed administrative services. The floor of the eastern stoa, which is better preserved, is covered with mosaics. These are divided in smaller sections and decorated with geometric shapes, different in each section. People gathered in these stoas to be protected by the weather conditions. Access to the double stoas was under control. Marble panels were put at the inter-collumniations, so that the visitors could enter in certain parts. The very first inter-collumniation of the southern stoa, because of its function ' to set up a marble door ' is larger than the others. Apart from the restored column, bases of some columns are rescued in their original positions, within a distance of about 2 meters from each other. They are of attic order and stand on square bases.

During the present phase of the excavation in the historical area of the Roman Forum, more replicas of the ancient marble bases and Corinthian capitals of columns have been constructed, which are exhibited in the area of the Square. Access to the narrow commercial street was also protected. The row of shops was discontinued by a double imposing door. The eastern opening led to the upper level of the south wing through a built staircase, whereas the western one led down to the Cryptoporticus.

On the southern side of the Square, due to the natural inclination of the ground, there was a construction of a double underground stoa with a vaulted ceiling (Cryptoporticus). It functioned as a foundation for the stoa and at the same time as a retaining wall of the additional technical filling with earth, made for leveling the big Square. In direct connection with the southern side of the Cryptoporticus, a row of shops created, where pottery and coppery products were made and merchandised. Their entrances faced a marble paved street, parallel to today's Fillipou street, which is saved along the south side. It was a narrow commercial street 2, 00 meters wide without the gutters and the pavements.

The Odeion is in the central part of the eastern side of the Forum, where at least three Roman working phases have been identified. Initially, in the centre of the eastern side of the Forum a roofed rectangular Bouleuterion with curved seats for an audience of about 200 people was constructed. In the late 2nd or early 3rd century A.D, due to the construction of an Odeion for an audience of 400 people, this room was demolished.

Access to the Odeion was possible through five marble doors. The outer ones were used only by the actors. The audience entered the Odeion through the three middle doors leading to an aisle under the stage and ascended the landing via two staircases, being at the end of the aisle. Due to the audience's difficult access under the stage, its front with the recesses was constructed fairly high. Consequently, for the sake of a better view the first tiers were constructed on the same level with the stage. As a result, an unusually high wall, named podium, was builded around the orchestra.

Around the middle of the 4th century, stoa's floors were decorated with mosaics and parts of the colonnades were restored. In the second half of the same century, probably during the time of the Julian, the Odeion extended and has been modified into a theatre. A second cavea, four times bigger in space, now for an audience of 2000 to 2500 people were constructed. Owing to the demands of the new theatre, the stage of the Odeion was extended to the west covering the width of the inner stoa but leaving completely untouched the columns on the west wall. The three central entrances which were initially used by the audience were closed and two new wide staircases at the end of the aisle led to a main landing, where the audience could go either to the old cavea or up to the new one. Only the two old entrances used by the actors remained. Only the north part of its foundation ditch at a distance of 4, 60 meters from the last round wall has been discovered. The Stoa of 'Images' of Thessaloniki, the southeastern entrance of the Roman Forum, on the side of Egnatia street, consisted of a big double colonnade, which was constructed in the era of the Seviri (220 ' 230 A.D). On its lower part there were columns with Corinthian capitals, while on the second floor there were six big sculptures, the famous 'Elgin' marbles of Thessaloniki. They had the form of two-faced pillars, depicting Mainada, Ariadni and Leda on one side and Niki, Avra, Dioskouri and Ganemedes on the other.

The whole complex comprised the glorious 'Stoa of Images', as the greek population of the town used to call it, which was mostly known by the Spanish-hebraic name 'Incantadas', meaning enchanted. These statues are associated with the local mythology as follows: while Great Alexander was heading with his troops towards Asia, he camped at the Roman Forum of Thessaloniki and he was enchanted by the daughter of the king of Thrace. He spent his nights under the Stoa of Images in order to meet the beautiful princess. The Stoa of Images has been described by many sightseers and is portrayed on the gravures of Stewart and Revett in 1792. It was kept almost intact until the 19th century in the yard of a Hebraic house. In 1865 it was taken apart and transferred to the Louvre museum by the paleographist Emanouil Miller. The relevant permission was given by the Turkish authorities of Thessaloniki, which was then under the Ottoman domination.