I have had the great fortune of being able to visit some of the western world's finest art museums: The Prado, the Louvre, the Uffizi, the Met, MoMA and a few others in Spain. To this day I can still feel the rippling thrill of seeing the subject of my college thesis, King Philip IV of Spain as painted by Diego Velazquez, peeking around a corner at the Prado. Nothing in this world can replace that.
But Google has unveiled the next-best thing. Now you can tour arts institutions and get ultra-close-ups of famous artworks through Art Project. A few years ago, it did something like it with the Prado, but now you can actually peruse the galleries themselves.
So, right now you can visit Madrid's Museo Thyssen-Bornemisza and Museo Reina Sofia (home of Picasso's "Guernica"). I'll probably be spending way too much time hovering over some gorgeous hi-res Van Goghs.
It's not perfect: there still seem to be a few kinks this morning (tip: refresh and cache often); learning to navigate the buildings is tricky; and some of the masterpieces, like "Guernica," aren't available scanned for close-ups. So for now I recommend using this to spend some quality time with the hi-res images of the art you can see.
With that, I give you a detail of Hans Holbein, the Younger's "Sir Thomas More," painted in 1527.