The fort of St Michael is situated on the prominent hill of the island of Ugljan off the coast of Zadar. This position is strategically important because it enables control of navigation in the entire Zadar archipelago, and this was the fort’s main role throughout history, especially during the period of conflict between Zadar and Venice. The fort owes its name to the Benedictine monastery which stood within the fort until the fifteenth century. The exact time of the founding of the monastery, or the construction of the fort, are not known. The fort is first mentioned in the Venetian chronicles of 1345 and 1346, when it was conquered during the siege of Zadar. After partial destruction, the fort underwent an intense renovation campaign in the second half of the fourteenth century. Late fourteenthcentury documents provide evidence about the building works on the main tower and houses for the crew which were carried out by the local builders: the Bilšić brothers and Nikola Arbusjanić. Fortification walls with five regularly-spaced towers form an irregular polygonal ground plan which was adapted to the terrain of the hill. The fort walls have been preserved to the height of the walkway with partially preserved castellations. The best-preserved parts are two south-western square towers with Gothic vaults composed of pointed arches, and the south-eastern portion of the walls with a walled-up entrance, defended by a massive main tower. The church of St Michael which stood at the centre of the fort was completely destroyed in bombing raids during the Second World War. Its modest remains, together with extant drawings and descriptions, show a small single-cell structure with a semicircular apse and indications of Gothic style evident in the pointed arches of the portal and windows. Its construction has been dated to the mid-fourteenth century. The fort has been well-preserved to date and represents the largest medieval fort on the Zadar islands.