For a comprehensive introduction to Dutch and Flemish Art, visit the Mauritshuis, a jewel-box of a museum in an old palace and brand-new wing. Almost every work is a masterpiece, among them Vermeer's Girl with a Pearl Earring, Rembrandts including a wistful self-portrait from the year of his death, 1669, and The Anatomy Lesson of Dr Nicolaes Tulp . A five-minute walk southwest, the recently restored Galerij Prins Willem V contains 150 old masters (Steen, Rubens, Potter, et al).
The main building was constructed as a mansion in 1640 in classical style; all its dimensions are roughly the same (25m), and the detailing shows exquisite care. In 1822 it was made the home of the royal collection.
Even if you're just passing through Den Haag on the train, it's well worth hopping off to visit.
