One of the most important churches of Mystras is the Cathedral of Agios Demetrios, built in 1280- 1292. It is the oldest church in the city.
This church has a mixed architectural style: on the one hand it has a three-aisled basilica with a narthex and a bell tower, built in the 13th century on the ground floor, and on the other hand, the upper floor is a cross-in-square church, added in the first half of the 15th century. Its interior is decorated with wall paintings in many different styles. This is where the last Byzantine emperor, Constantinos Paleologos, was crowned in 1449.
References:The first written record of church in Danmark locality date back to the year 1291. Close to the church are several stones with a Christian text and cross inscribed. The oldest parts of the present red-brick church are from the 1300s. In the late 1400s the church was enlarged to the appearance it has today. The church has been modified both internally and externally several times, among other things after the fires in 1699 and 1889. There are lot of well-preserved mural paintings in the walls.