The oddly named 18th century 'Aa church' is a beautiful brick building that stands on the spot of several earlier versions, that suffered an unfortunate series of demolition, fires and gravitational setbacks. It lost its religious function decades long ago and it's used for exhibitions, events and parties nowadays. The 76-metre high tower with its distinct yellow balconies rises up over the nave and choir, which are a metre higher than those inside the Martini church. Group tours of the building (€50 for up to 15 people) can be requested, and go up into the roof, but not up the tower.