Oosterkerk is a Gothic church on Hoorn's old harbour side, with roots in the 15th century and a building largely dating from 1616. It began as a Roman Catholic church and later became Dutch Reformed after the Reformation.
The church was nearly lost after it fell out of regular use in the 1960s, but it survived and now serves as a venue as well as a place for Sunday services. It is a worthwhile stop for visitors following Hoorn's historic waterfront and Golden Age streets.