This is a pretty interesting and unique site, but one that is a bit challenging to visit. It consists of over 30 separate sites within a 15 to 20-km radius around Amsterdam, all in various states of repair, with many not accessible to the public. The highlight is the small (artificial) island of Pampus in the IJsselmeer, which can be reached by ferry from Muiden. The military and civilian installations there are still very impressive and give a good idea of what life was like for the soldiers stationed there (it was only fully staffed during WW I). The guided tours seem to be in Dutch only, but you can get a map and walk around on your own. The pretty port city of Muiden has a nice maritime atmosphere and features, besides the interesting Muiden Castle, another part of the WHS - the Muizenfort, which includes some well-preserved trenches. The West Battery is directly opposite the castle and can be seen from the ferry (it would be a very long walk there). In the nearby town of Weesp (where the buses to Muiden leave), I went to see the Fort aan de Ossenmarkt, which looks quite impressive and well-preserved from the outside, but can't be visited. These sites are all southeast of Amsterdam and seem to be the ones that can be visited most easily. After my visit to Beemster (north of A'dam), I went to the nearby town of Edam, which is most famous for its cheese-making tradition. The Fort bij Edam can be reached in a (very) long walk from the centre. It is only open on selected days (first and second Sundays of each month from April to October, and afternoons only), because it is run and staffed by volunteers. It is not in a very good shape, but it was still interesting to walk around in the dark alleys and small exhibition rooms. Apart from Amsterdam's canal area, this was the most interesting WHS I have yet seen in the Netherlands.