The Sint Janskerk in Hoorn is the oldest existing building on the island. The building dates back to the 13th century. The structure has a small, heavy tower on the west side. Around the church is a cemetery that is still used as a cemetery. Between 1963 and 1969 the church was restored. In the room under the tower, objects such as coins and building fragments can be viewed that were found in the soil during the restoration. The church is a national monument. At the church is the Sjouw, also called 'time ball', a ball that was hoisted to let the working people know that it was time to go home for lunch.