Muiderberg, part of Muiden municipality, is the home base of Mock's City Views. The seaside village, built on a sand ridge, was first mentioned in a document around 1280, when Floris V was lord of Muiden and Muiderberg. Its major landmark is the reformed Kerk aan Zee, Muiderberg's oldest building. Muiden celebrated its 1050th anniversary in 2003, with many events taking place around the great locks linking the Vecht and the IJsselmeer. At the mouth of the Vecht lies the famous Muiderslot castle, commissioned by Floris V around 1280.