The Katedrala Sv. Tripuna is located on the square in Kotor of the same name. It's the cathedral of the Kotor Catholic church.
In the IX century there stood a small church housing the remains of St. Tryphon, bought out by citizens of Kotor from the Venecians. Construction work started in 1124 and only finished in 1166, which is when the cathedral was christened after St. Tryphon.
Through the years the cathedral was rebuilt several times, including in 1667 and 1979 after earthquakes. It was most recently rebuilt in 2003, after which the cathedral and the entire Old Town were named UNESCO's world heritage site.
The cathedral is an example of Roman architecture. You can see partially preserved frescas from the XIV century, as well as marble pillars and scultures, the marble altar created by Venecian masters in the XVIII century, bas-reliefs depicting St. Mary and scenes from the life of St. Tryphon. His remains are also kept there.
The cathedral is open for tourists, admission is 3 Euro. It also houses the Museum of sacral art.