The Google Cultural Institute was launched in 2011. It currently contains over 6 million items including photos, videos and documents.
I have to say, the Google Cultural Institute is absolutely A-MA-ZING! There are exhibits and collections from museums and archives from around the world. You can also create your own galleries.
On the home page, you'll find link to the Google Art Project, Historic Moments and World Wonders. Each of these contain their own content including high resolution images (you can zoom in so close you can see the brush strokes in a painting), historical photos and documents and unbelievable views of historical buildings.
Take a few minutes (or an hour or so) to visit this site - you'll be so glad you did.