This is wonderful! I don't know where to go first!
"Google Arts and Culture has partnered with more than 2,500 museums and galleries around the world in order to offer virtual tours and online displays of their collections to internet surfers."
Click a museum page and scroll down to the "Museum Views" bit for the "streetview" style walk through. There are also photo galleries stuffed with thousands of exhibits you can click through.
www.goodnewsnetwork.org/tour-2500-world-famous-museums-from-comfort-your-own-sofa