The Reformed Church in the fortress is the most important medieval monument in Târgu Mureș and the only one preserved since the beginning of the 15th century. It originally housed a Franciscan monastery and the first known mention is from 1332.
The church is built in the Gothic style, it is located on a terrace of the river Mures, at the southwestern tip of this terrace, which is part of the hill called Cornești plateau. The component buildings were grouped around a rectangular interior courtyard. From the monastic complex were preserved the church, the tower, the sacristy and the altar of the chapel.