Hidden inside the Rijksmuseum, the Cuypers Library is the oldest and largest art history research library in the Netherlands. The reading room is spectacular — a soaring vaulted space designed by Pierre Cuypers (the same architect who designed the museum itself and Centraal Station), with ornate ironwork balconies, spiral staircases, and natural light pouring through the glass ceiling.
The library is a working research facility, not a museum display, but it is open to visitors and you can walk through freely as part of your Rijksmuseum visit. Most people rush past it toward the Night Watch — slow down and look up. The room has been beautifully restored to its original 1885 appearance. Photography is allowed. It is one of the most beautiful library interiors in Europe, and one of the Rijksmuseum's best-kept secrets.