• Amsterdam Castle Muiderslot is the oldest castle in the Netherlands, and part of the Amsterdam Defence Line, a World Heritage Site Amsterdam Castle Muiderslot is not just the oldest castle in the Netherlands. It is a magical place, surrounded by water and vegetation. The castle gardens feature lots of heritage varieties: vegetables, herbs, fruit, herbaceous plants and flowers (some of them edible). The produce from the gardens was for centuries used to prepare the exquisite meals at the castle. And the gardens still produce a rich harvest every year. Muiderslot is also part of the Amsterdam Defence Line, a World Heritage Site. The castle gardens are open daily, offering visitors the chance to enjoy this lush part of our heritage.