Split is situated on a peninsula between the eastern part of the Gulf of Kastela and the Split Channel. A hill, Marjan (178 m), rises in the western part of the peninsula. The ridges Kozjak (780 m) and Mosor (1,330 m) protect the city from the north and northeast, and separate it from the hinterland. Split has a Mediterranean climate: hot, dry summers (maximum air temperature in July reaches 36°C) and warm, wet winters (average annual rainfall is 900 mm). Split is one of the sunniest places in Europe. Vegetation is of the evergreen Mediterranean type, and subtropical flora (palm-trees, agaves, cacti) grow in the city and its surroundings. Marjan is covered with a cultivated forest.
Although the beginnings of Split are usually linked to the building of Diocletian's Palace, there is evidence that this area was inhabited as a Greek colony even earlier.).

Roman walls in SplitDiocletian was a Roman emperor who ruled between AD 284 and 305 and was known for his reforms and persecution of Christians. He ordered the work on the palace to begin in 293 in readiness for his retirement from politics in 305. The palace faces the sea on its south side and its walls are 170 to 200 m (570 to 700 feet) long and 15 to 20 m (50 to 70 feet) high, and it encloses an area of 38,000 m² (9½ acres). This massive structure was long deserted when the first citizens of Split settled inside its walls. In 639, the interior was converted into a town by the citizens of Salona who escaped the destruction of their town by the Avars. Over the centuries, the city has spread out over the surrounding landscape, but even today the palace constitutes the inner core of the city, still inhabited, full of shops, markets, squares, with even a Christian cathedral (formerly Diocletian's mausoleum) inserted in the corridors and floors of the former palace. Although part of Byzantine Empire, the town had political autonomy.

The rise of the Medieval Croatian state in the hinterland provoked in the following centuries a slow Croatization of Split, which can be seen in the architecture of churches in the city and surroundings, and which led to the unity of the church with Split at the center in 928; it is important to mention that there was a big church synode, where a clerical jurisdiction over Croatia and relations of latin-rite and croat (slavic)-rite in church in Croatia were discussed.

At that time Split was also the capital city of medieval Croatian duchy and later, kingdom; Croatian duke/king ruled from this city, as well as from some other nearby townlets: Solin, Klis, Biaći and Omiš.

On the peninsula, position on the west of the southern city port there was a medieval benedictin monastery of "St. Stephen under pines" (San Stephanus de Pinis), or in Croatian "Sveti Stipan pod borima". The peninsula got the name after that monastery - Sustipan. Most famous inhabitant of that monastery was the son of Croatian king Demetrius Zvonimir (in Croatian: Dmitar Zvonimir), Stephen (in Croatian: Stipan). The founder of that monastery was the archbishop of Split, Lovre (in English: Lawrence), a big friend of the king Zvonimir. The monastery was founded in 1069.

Narodni Trg (Pjaca) in Split
At the beginning of the 12th century Split was led by Hungarian nobility. The city however mantained independence, as in 1312 it issued statues and had a currency of its own. The Venetian Republic took control of Split in 1420, when the population was almost exclusively Croatian. The autonomy of the city remained, though somewhat reduced: the highest authority was a prince-captain who was always of Venetian birth.

During the Middle Ages and under Venetian rule Split developed into an important port city with trade routes to the interior through the nearby Klis pass. Culture flourished as well, Split being the hometown of Marko Marulic, a classic Croatian author. Marulic wrote Judita (1501) in Split, and published it there (1521). It is widely held to be the first modern work of literature in Croatian.

Venice held Split until its own downfall in 1797. The city fell to Austria-Hungary after a brief period of Napoleonic rule (1806–1813). Under Austria, however, Split stagnated. The general upheavals in Europe starting in 1848 gained no ground in Split.