The astronomical optical illusion/art installation in the Hague known as the Celestial Vault is a curious location that is equal parts Druidic stone altar and stark modern landscaping which allows those willing to interact with it a chance to see the heavens in a new way.
Built in 1996 by artist James Turrell, the Celestial Vault is a monumental earthwork built up to resemble a large crater. After entering the crater via a curved tunnel that runs through one side, visitors will find nothing but a lush, grassy interior and an odd stone bench in the very center. The stone is flat on top and slightly peaked so that there are two identical sloping planes. The idea is for visitors to lie on the slabs with their heads towards the lower ends of the slopes which will allow them to see the edge of the crater but mainly the open sky. With the curved edge as a reference point the sky appears to be a curved dome (which it sort of is).
This optical illusion was inspired by the findings of a Belgian astronomer who noted how light affects our perception, and now anyone in the area can find out how true that is for themselves.
Today the work is not as sharply manicured as it was in the late 90s with overgrown foliage and other blemishes marking the crater slopes, yet the immovable bench remains in perfect working order, just waiting for people to expand their minds.