Church of St. Križa

The Cathedral of the Assumption of Mary is a Romanesque church dating from the 11th century. Hardly anything is known about the cathedral before the year 1000, although in Koper, with interruptions, bishops have been enthroned since 520. The oldest mention of the Romanesque Church of Mary in Koper dates back to the end of the 11th century. The church houses the relics of St. Nazarius and St. Alexander.

The origins of the Church of the Holy Trinity are debated (12th or 15th century), a debate fuelled by the building's strange architectural style. However, its defensive nature leaves no doubt. Embedded in a thick wall and surrounded by two towers, the church was a protection against Turkish attacks in the region, frequent in the 16th century. Inside, magnificent medieval frescos representing a Danse Macabre are still preserved.

The Church of Saints John and Paul was built in the 15th century on the remains of an earlier sacred building with three apses that was consecrated in 1263. The church was completely remodelled between 1444 and 1467. The Romanesque building was enriched by covering the façade with white stone slabs, thus giving the building a Gothic-Venetian style.