Because I had limited time in and around Amsterdam when visiting in 2014, I concentrated on a section of the Defense Line just outside Haarlem, which included Fort Liebrug and Fort Penningsveer. The walk to the forts was scenic, bypassing a recreation area on the west side of the Liede River. Both forts are on the east bank of the Liede. Fort Liebrug was closed, so I only got to see it from the road, but Fort Penningsveer was open on a Thursday afternoon in the summer. Fort Penningsveer is tree-covered and surrounded by a moat, and has several earth-covered bunkers and trails to explore. I encountered a youth camp unexpectedly on the back side of the fort, but I later found out on the Defence Line of Amsterdam website that the fort is being used for educational camps. The forts weren't the most breathtaking World Heritage Sites I've seen, but they were a pleasant way to spend a summer afternoon.

Logistics: Train to Haarlem Spaarnwoude station (near Haarlem IKEA); walking path to the east bank of the Liede River to find both Fort Liebrug and Fort Penningsveer.