Complex sentence: In medieval times Rijeka acquired its Croatian name, "Rika svetoga Vida" ("the river of St. Vitus") when it was a city surrounded by a wall and was thus a feudal stronghold.
Split into simpler sentences: In medieval times Rijeka acquired its Croatian name, "Rika svetoga Vida" ("the river of St. Vitus"). Medieval Rijeka was a city surrounded by a wall and was thus a feudal stronghold.