The development of Rijeka encouraged the newly settled Slavic population – the Croats – to occupy Tarsatica and start forming a new settlement. The first original news about the medieval settlement comes from the first half of the 13th century. century, but then two settlements appear in historical sources: TRSAT, on the hill on the left side of the Rječina, on the site of the Liburnian settlement TARSATE, and RIJEKA, on the coast, on the site of the Roman TARSATICA. Ta Rijeka is a fortified town, surrounded by walls with several defensive towers, divided into two parts: the upper one has a medieval castle and the church of St. Vida (hence the name Flumen Sancti Viti) and the lower folk, trade and craft settlement among whose residents the usual name is Rika or Rijeka.
At the beginning and end of XIV. century Rijeka was in the possession of the lords of Devin, the princes of Krka (the latter Frankopans), then in the possession of the Walsee family, and from 1466 Habsburgs. At that time, Rijeka had about 3,000 inhabitants. A significant economic boom began in the 16th century. in addition to trade in iron, oil, wood, wool, livestock and leather. In the XVI. century, there is also a printing house in the city with the Croatian script – Glagolitic. At that time, there was no settlement (Sušak) on the left bank of the Rječina below the settlement of Trsat, it was formed only in the 18th century.
The golden age of Rijeka’s trade suddenly waned in the second half of the 15th century. century. Frequent Turkish raids cut off transport routes, as well as wars between pretenders to the Hungarian throne and long-term conflicts between the Uskoks and the Venetians. The calming down of war conditions began in the second half of the 17th century.
The arrival of the Jesuits in Rijeka and the establishment of their high school significantly improved the educational and cultural life, while strengthening Romanism at the expense of the Croatian language and Glagolitic. The Rijeka economy began to gain a significant advantage in the 18th century. Then the emperor Charles VI. declared Rijeka a free port, but soon Hungary, strengthened as part of the Habsburg Monarchy, began to look at Rijeka as its exit to the world. At the turn of the XVIII. and XIX. century Rijeka is under French administration, and after that again under Austria.