The Groeningemuseum is Bruges' essential art museum, home to a world-class collection of Flemish Primitives that you simply cannot see anywhere else in this depth. Jan van Eyck's Madonna with Canon Joris van der Paele and works by Hans Memling, Gerard David, and Hieronymus Bosch anchor a collection that traces painting in the Southern Low Countries from the 15th century to the present.
Just across the lane, the Gruuthusemuseum occupies a medieval merchant's palace and covers daily life in Bruges through furniture, tapestries, and silverwork. A few minutes further, the former Sint-Janshospitaal -- one of Europe's oldest surviving hospital buildings -- now houses the Memling Museum, with six intimate masterpieces by Hans Memling painted for the hospital itself.
You can visit all three in a single morning. The Groeningemuseum is small enough to absorb in an hour without feeling rushed.