There are many museums in the Netherlands that have medieval objects in their collections. A small selection:
Huis Bergh, ’s-Heerenbergh
Languages: Dutch, English, German
Situated on the German border, this castle contains a significant art collection, among which many works from the later middle ages.
Museum Boijmans van Beuningen (Rotterdam)
Languages: Dutch, English
This museum has large art collections, among which a fine collection of fifteenth and sixteenth century panel paintings
Museum ’t Catharijneconvent (Utrecht)
Languages: Dutch, English
This Museum of religious art has one of the largest collections of medieval art in the Netherlands: panel painting, sculpture, manuscripts, etc.
Museum Meermanno-Westreenianum, Den Haag (The Hague)
Language: Dutch
Museum of the book, founded with the collections of the 18th-19th century barons Meerman and Westreenen. Houses especially an important collection of medieval manuscripts and incunabula.
Museum Mauritshuis, Den Haag (The Hague)
Languages: Dutch, English
Very nice collection of 17th century Dutch painting, containing also some 15th and 16th century ones, such as Rogier Van der Weyden’s Lamentation.
Rijksmuseum (Amsterdam)
Languages: Dutch, English
National museum of art (until the nineteenth century), includes a fine collection of panel paintings, sculptures and other objects from the fifteenth and sixteenth centuries.
Rijksmuseum van Oudheden (Leiden)
Languages: Dutch, English
National museum of antiquities, especially known for its antique collections (Egypt, Greece, Rome), but also comprising a fine department of medieval archaeology.
Museum voor Religieuze Kunst, Uden (Brabant septentrional) (Museum of Religious Art)
Museum founded in the building of a Convent of Birgitine Sisters (still present under the same roof), housing a collection of religious art of the Netherlands ; some medieval pieces.
Two of the best preserved medieval castles in the Netherlands are the Muiderslot and Slot Loevestein.