Hellevoetsluis is a small fortified town on the island of Voorne-Putten in South Holland, sitting where the Haringvliet meets the North Sea. For centuries it served as the main naval harbour of the Dutch Republic — William III of Orange sailed from here to claim the English throne in 1688. The old fortifications, dry dock, and naval buildings still ring the harbour basin, giving the town centre a character quite unlike the modern suburbs that surround it.
The restored Droogdok, the oldest dry dock in the Netherlands, is the centrepiece of a small maritime quarter with a lighthouse and a fire ship museum. You can walk the full circuit of the star-shaped fortress walls in about half an hour, with views over the harbour and the Haringvliet. The town is also the starting point for cycling routes across Voorne-Putten and along the Delta Works dams.
Hellevoetsluis is not a place you would spend a whole holiday, but it makes a pleasant half-day stop if you are exploring the South Holland coast or the Delta region. There are a few cafes around the harbour, a weekly market on Saturdays, and enough maritime history to keep things interesting.