The 12th-century Holy Trinity Church in Hrastovlje was fortified in the 1500s to defend it against Turkish attacks. The high defensive wall which surrounds the church means that from a distance only the top of the tower can be seen peeking out above the walls. Inside, the church hides a beautiful secret.

Hidden beneath thick layers of plaster, nearly perfectly preserved medieval frescoes were discovered in 1949, covering almost every inch of the walls and ceiling of the church. The artworks were completed in 1490 and have remained unchanged ever since.

Among the paintings is a rare and pristine example of the Danse Macabre, or Dance of Death, which depicts characters from all walks of medieval life being led by skeletons to the grave. This painting served to remind the people of Hrastovlje of the fragility of life and universality of death.

Among the paintings on the church walls you can also see markings in the now-extinct Glagolitic script, a very early Slavic writing system.