Saint John's Fortresss, Stone fortification in Šibenik, Croatia.

Saint John's Fortress is a stone fortification built on a hilltop above Šibenik that overlooks the coast. The structure features thick walls, bastions, and connected chambers that were carved into the rock.

St. John's Fortress was built in 1646 during the Cretan War, after Šibenik's citizens had petitioned Venice for hilltop defences since the 1520s. The Genoese engineer Antonio Leni designed it, and work began on 1 August 1646, finishing in 58 days. In 1647 its defenders repelled an Ottoman army of about 25,000 during a month-long siege.

The name Tanaja comes from the tenaille, the plier-shaped outwork on the north side. The citizens of Šibenik built the fortress themselves in 1646, after the Venetian senate refused funds but did not forbid the work. In August and September 1647 around 7,000 defenders held off some 25,000 Ottoman soldiers; about 4,000 attackers died.

You can walk up to the site and enjoy views of the city and sea, especially in early morning or late afternoon light. The access is fairly straightforward, but the paths are steep, so allow time for the climb.

The fortress's local name, Tanaja, comes from its plier-shaped outwork, the tenaille (Italian tenaglia), on the northern side. The star-shaped plan was drawn by the Genoese Franciscan engineer Antonio Leni, and the whole fort was finished in just 58 days, from 1 August 1646.