In this nucleated village you can find the famous Holy Trinity Church, which is hidden behind a defence wall that was erected at the end of the 16th century.
The inside of the three-nave Roman church with a barrel vault and high bell tower is decorated with Gothic paintings from 1490 and they are the reason Hrastovlje is classified at the top of the treasure trove of mediaeval wall paintings in Slovenia.
The frescoes are the work of Janez of Kastav and were discovered in 1951 by Jože Pohlen. The frescoes depict the creation of the world, expulsion of Adam and Eve from the garden of Eden, scenes from the suffering of Jesus, work of farmers in various seasons and the famous Dance of Death. The latter is the most famous part of the frescoes and represents an extraordinary achievement of medieval iconography. Beside the frescoes, there is also the Glagolitic inscription.