Visit: Art Institute Of Chicago
Copyright: CC0
The Art Institute of Chicago is home to some of the world's most revered masterpieces, including more than 50,000 pieces in its public domain collection, which are free to use and open to commercial use. From renowned icons like van Gogh and Picasso, to lesser known but no less amazing artists, like Pointillist painter Paul Signac (a friend and former student).
The Art Institute has one of the better organised websites. You can explore thousands of works from all around the world and learn about different cultures at your own pace by searching and filtering their public domain collection - which houses some masterpieces you'll recognize instantly - or have a tonne of fun discovering for yourself!