During periods of cold, boat traffic is blocked from certain canals (usually Keizersgracht en Prinsengracht) to allow the water to freeze.
See Also
Why Shrink the Rink? | JLG ArchitectsWinter Olympic Games - TIMERoller Planet Amsterdam - Get your groove on! - Race PlanetIce skating in California Thanks to Synthetic Ice | Glice Eco RinksSkating on the canals of Amsterdam to the strains of classical music is a memorable experience. Little kiosks are set up on the ice to dispense heart-warming liqueurs.
Go cautiously when skating under bridges, where the ice is usually thinner, and in general don't go anywhere the Dutch themselves don't.
