Also known as the Castle Church, the oldest building of the city was originally built between 1241 and 1283. Its present day plan was finalised when it was rebuilt in Gothic style in the 14th century. It was again renovated, this time in a Baroque style by the Zichy family in 1710. Its present day outlook was completed between 1742 and 1751.

The building is 200 m2 large, its tower is 29 meters tall. Its walls are supported by buttresses which are typical to Gothic architecture. On the buttress near the tower, there is a sun clock from the 1300's, a unique piece from the history of Hungary. The visitor can step inside the church through Gothic stone doors.

Looking up in the interior of the building, we can see three giant, Baroque rib vaults. The three side altars are dedicated to the Virgin Mary, Three Kings and Saint Andrew. The main altarpiece depicts the Baptism of Jesus by Saint John. The painting is a work of Carolus Schöfft from 1818. Above the altar an all seeing eye watches over the church. Interestingly, the biblical figures of the frescoes, instead of the usual, authentic settings, are depicted in the landscape of Szentendre.