The mainly flat land gradually slopes toward the sea along the shoreline, which is scored with shallow valleys with microclimates favourable to the flourishing of flora and fauna.

The city extends inland toward the municipalities of Corato, Ruvo di Puglia, and Terlizzi, where it reaches the foothills of the Murge Plateau.

The oldest part of the city, once bounded by two valleys that converge near the basin of the port, sits higher than the later surrounding urban development.

[10] According to Mario Cosmai, author of a number of local histories of the town, "Pompeo Sarnelli theorized that Bisceglie was founded by the Romans at the time of the Pyrrhic war.

[13] Evidence of human activity is found in numerous flaked stone weapons and tools, remains of animals of extinct species such as prehistoric lions, bears, oxen and horses, remains of animals of remote species like rhinoceros, hyena, and deer, and the curved human femur typical of Neanderthal man found in the grotto of Santa Croce that is currently preserved in the National Archaeological Museum of Taranto.

The Chianca dolmen (from the local dialect word 'chienghe', or stone slab[citation needed]) has a 10-meter long passage leading to a burial cell of 2 x 1.6 meters.

[14] When the central part of Puglia was supposedly occupied by the Peucetians, a theory not supported by sufficient archaeological evidence, the area of the prehistoric sunken Karst basin that forms a wide natural amphitheater in Molfetta, and the district of Navarino in the territory of Bisceglie, were home to Greek settlers who had left their native lands of Pylos and Nabàrinon in Greece.

[16] In the third century, following the Pyrrhic War, the territory fell under the dominion of Rome, and even though furrowed by new roads, it continued to be a transit zone and a place of scant importance.

At the fall of the Western Roman Empire, the territory of Bisceglie was characterized by the presence of small clumps of houses surrounded by high walls that were often adjacent to religious temples.

The Giano (Janus) farmhouse dating back to the Roman age, and the hamlets of Cirignano, Pacciano, Sagina, and Zappino are all known for this type of house.

There was a spot there along the coast, rough and dense with vegetation, that was a good shelter for boats that was called by the inhabitants Vescègghie, from the name of the wild oaks spread all around.

In 1167 Bishop Amando ordered the transportation of the sacred relics, kept until then in a sepulcher in the hamlet of Sagina, to within the city walls where the cathedral building had been completed.

In 1324 it passed to Amelio del Balzo and later, in 1326, to Robert of Anjou, son of King Charles II of Naples and his brother Philip.

Despite the period of thriving commerce with the ports of the Adriatic and beyond, the young city was at the heart of intricate and bloody struggles that tore Puglia apart under Joanna I of Naples.

After their martyrdom, their remains were transported to the Bisceglie area in the Sagina district, where a Christian widow, Tecla de Fabiis, placed them in a tomb that she had had built.

On 9 June 1167, under the bishop Amando, the sacred relics of the three martyrs were transported inside the walls of Bisceglie, and initially kept in the church of San Fortunato, near the castle.