The Binnendieze is a network of rivers and canals that runs through and underneath the historic centre of Den Bosch, passing below streets, under house foundations, through arched tunnels, and occasionally emerging into daylight before disappearing again. A guided boat tour is the only way to see most of it, and it is one of the more unusual things you can do in the Netherlands.
The tour lasts about 75 minutes and covers the most atmospheric sections, including long passages where the canal runs through low brick tunnels beneath buildings, with the ceiling inches above your head. Commentary explains the history of the waterway and its role in the city's medieval economy. Tours run regularly from April to October and can be booked at the departure point near the Parade square.