In fact, Naarden is one of the best preserved fortified towns in Europe today.
But defense works on Naarden were old and poorly maintained.
At this time the Netherlands were an important economic and political power in western Europe.
They captured Utrecht and made it a base to invade the rest of the country from.
In 1673 Naarden was back in Dutch hands.
After this recapture the fortifications were updated to modern standards.
Photo credit
Most of the fortifications that exist today date from this period.
Instead, emphasis was given on bomb shelters most of which still exist.
After the First World War the need for Naarden as a fortress was over.
Tours are provided by boat around the lake.
Naarden on Google Earth
Sources:1,2