[5] There is only limited archaeological evidence from the city's foundational period as there were almost no traces left of the Celtic town, except for some burial sites with grave goods - the necropolises found at the locations in the modern neighborhoods of Karaburma and Rospi Ćuprija.

[5] The Celtic fortification was a primitive one, located on top of Terazije ridge, above the confluence of the Sava into the Danube, where Belgrade Fortress still stands today.

For singi- there are several theories including those that it is a Celtic word for circle, though the only word with a similar form recorded in other Celtic languages is Old Irish seng "narrow, slender, good-looking; ant" (Modern Irish and Gaelic seang), hence "round fort", or that it could be named after the Sings, a Thracian tribe that occupied the area prior to the arrival of the Scordisci.

[8] Another possibility is that it is a composite name the first part of which (Sin-gi) means "Old prayer" ("sean guí" in modern Irish), implying that this was originally a site of Celtic religious significance, in addition to becoming a fortress (dun).

In 75 BC, Gaius "Quintus" Scribonius Curio, the proconsul of Macedonia, invaded the Balkan interior as far as the Danube, in an effort to drive out the Scordisci, Dardanians, Dacians and other tribes.

It wasn't until the rule of Octavian, when Marcus Licinius Crassus, the grandson of the Caesarian Triumvir and then proconsul of Macedonia, finally stabilized the region with a campaign beginning in 29 BC Moesia was formally organized into a province some time before 6 AD, when the first mention of its governor, Caecina Severus, is made.

Early Singidunum reached its height with the arrival of Legio IV Flavia Felix which was transferred to the city in 86 AD and remained there most of the time until the mid 5th century.

The presence of Legio IV prompted the construction of a square-shaped castrum (fort), which occupied Upper Town of today's Belgrade Fortress.

Construction began at the turn of the 2nd century AD as since the early 100s, Legio IV Flavia Felix became permanently stationed in Singidunum, except for a break between 108 and 118/9 at Bersobis.

Connecting this way Via Militaris with the western parts of the empire, Singidunum became a major crossroad, not only for the local provinces (Moesia, Dacia, Pannonia, Dalmatia).

It also became a seat of the bishopric,[5] and was a major center of Arianism until late in the century, with its bishops Ursacius and Secundianus leading local resistance against Nicene Christianity until the First Council of Constantinople in 381.

Other remnants of Roman material culture such as tombs, monuments, sculptures, ceramics, and coins have been found villages and towns surrounding Belgrade.

[18] In the area bounded by the modern Karaburma, Rospi Ćuprija and, at that time island, Ada Huja, Romans cultivated grapevines and used thermal springs for public bathhouses.

[22][23] Well preserved bust of emperor Macrinus (ruled 217–218) is discovered in modern village of Boleč, halfway between Belgrade and Brestovik, and close to the ancient Tricornium.

A 258 AD ceremonial breast plate with stylistic illustrations belonging to Legio VII Claudia soldier Aurelius Herculanus has been found[24] and many other artifacts of the Roman period such as silver coins that were washed ashore once the dam of the Iron Gate I Hydroelectric Power Station was constructed.

[5] The top of the Avala mountain proved to be suitable for building, so the Romans built a fortified outpost, probably on the foundations of the older Celtic one.

[25] Apart from guarding and controlling the access roads to Singidunum, the outpost was also important for the protection of the numerous mines on the mountain, which were exploited by the Romans.

In the 1970s and 1980s, experts from the National Museum in Belgrade explored the area and discovered many mining necropolis, centered around the villages of Babe, Stojnik and Guberevac.

[27] In 1963, a tractor which was plowing the land in the neighborhood of Zemun Polje, in the vicinity of Školsko Dobro's central building began digging up on the surface the old coins, head of a sculpture, pottery pieces and numerous other objects.

The previously unknown settlement was squarely shaped with the sides of 3 km (1.9 mi) and, at the time of discovery, was the largest known "outer suburb" of Singidunum.

[28] In the 5th and 6th centuries, Moesia and Illyricum suffered devastating raids by the successive invasions of the Huns, Ostrogoths, Gepids, Sarmatians, Avars, Slavs[1] and Herules.

The Slavic settlement obviously existed for a while as the new name was evidently accepted, while the city was a seat of a bishopric since the pope mentions episcopatus Belogradensis ("bishop of Belgrade").

The materials found in the tombs include pottery fragments and vessels, pieces of terracotta and stone statues, fan-shaped floor tiles, bronze and bone needles, bricks, rushlights, etc.

The remains were discovered during the construction works in the 1930s when the Brankova Street was extended to the Sava river, to make a connection to the future King Alexander Bridge.

Further discoveries in the area during the Interbellum include a golden polyhedron shaped earring from the early Middle Ages (Great Migration Period), found in Kamenička Street.

[34] On the crossroad of the Gospodar Jevremova and Kneginje Ljubice streets, in Dorćol, a house of worship dedicated to the Greek goddess Hecate, a sort of "descent to Hades", was discovered in 1935.

The forum, which included the temples of Jupiter and Nemesis, was located close to the Cathedral Church, where the modern building of the National Bank of Serbia in the Kralja Petra Street is situated.

[6][11] The northern section of the Academy Park, on Studentski Trg, was excavated in 1968 during the building of a furnace oil tank for the boiler room of the Belgrade's City Committee of the League of Communists located nearby.

In 2007, on the location of the former kafana Tri lista duvana at the corner of Bulevar Kralja Aleksandra and Kneza Miloša street, several necropolises were found.

In 2008 in Čika Ljubina Street remains of the house from the 4th century was discovered, which included the part of the floor and doorstep of the main entry door.