A land art installation by James Turrell, hidden in a crater-shaped bowl in the dunes near Kijkduin. You walk down a path into a grassy depression, lie down on an elliptical stone bed at the centre, and look up. The curved edges of the crater frame the sky in a perfect oval, and something strange happens: the sky appears to curve down toward you like a dome, an optical illusion created by the geometry of the surrounding walls.
The effect is strongest at twilight, when the sky deepens and the vault illusion intensifies. Turrell is known for his sky-observing installations worldwide, and this is one of the most accessible — free, outdoors, and open at all times. The walk through the dunes to reach it is pleasant in itself. Located in the Kijkduin area on the coast, about 8 km from the city centre. Bring a blanket and time your visit for sunset.