Few people are aware that auction houses such as Christie's have preview days before the actual auction happens. This is a great opportunity to just walk in (really you can just walk in) and have a look around. It is almost like an ever-evolving museum. One weekend you might have a chance of seeing a collection of Post-War masterpieces, whereas the next it could be an incredible array of medieval illuminated manuscripts. Sometimes there may even be multiple auctions on view so you get three different exhibitions in one! Most of these items have come from private collections and may be bought by private collectors so this is an excellent opportunity to see works of art in real life that you may never get to see again! And the best part of it is: it is completely free!