I visited one of the locations in August 2017. I was hoping to see more locations during my recent visit in November 2024, but unfortunately, I didn't get to visit any (it was raining and the wind was extremely strong). 

In 2017, I visited Fort Diemerdam just outside Amsterdam. I was staying near Amsterdam Centraal. I took the #26 tram to the IJBurg stop and walked the rest of the way (about 15-20 minutes). Fort Diemerdam has a few bunkers left on the site. The site is now an events venue. Near the bunkers, there is now a pavilion (Paviljoen Puur). There was an event happening at the time I went, so there were quite a lot of people near the pavilion, but there were still a lot of bunkers to explore away from it. The pavilion looks pretty cool, though - looks like a shell. 

Along with the not-so-great weather, I was also with my girlfriend the last time I was in Amsterdam. While I enjoy looking for UNESCO World Heritage Sites, this isn't for everybody, and the Dutch Water Defence Lines locations are not exactly a must-visit on any traveler's list. Also, I'm using the World Heritage - UNESCO List app, and the app only lists 9 locations. It's good to know that this site shows more locations.