I am a huge fan of house-museums, and although this actually was built to be museum, it has a real sense of place. I know someone related to the architect who designed this, and it's just fascinating that they knew they would have all this medieval art plus architectural art and were able to design a museum around it that feels like it's the real deal (you feel like you're in a castle, or a church/cathedral, or, natch, a Cloisters). The Treasury has wonderful works in gold and ivory, illuminated books, fabulously embroidered vestments, etc. The unicorn tapestries capture the imagination of children. In summer they have a lovely cafe where you can eat in the courtyard (be aware if visiting during the off-season that there is no where near to get any food). Also MUCH less crowded than the main museum. Note that with admission to the Cloisters you may also visit the main Metropolitan Museum on the same day (keep your receipt and pin). If you love the Cloisters and plan to visit Paris, don't miss the similar Musee de Cluny.