Louvre Museum, Paris

TL;DR: If you like art or history at all, plan for at least two days here, and a week to see it all. I have two strategies to recommend: Sightseer and eavesdropper. Eavesdropper - goes to learn the history or details about the art; not necessarily to sketch or relax. Go around peak busy times. Watch for tours in a language you understand and shadow them, calmly walking along. This lets you hear the lectures without being tied to a specific schedule. It is not illegal, but you may be asked to move on. Do so. Just explore on your own until you find another exhibit you want to know more about, and wait. Another lecturer will come along in time to explain that piece. Remember that some are more popular than others. Sightseer - goes to see the art in peace. Check Google Maps' busy times to see when most people go, and try to plan for when they are not there. If that is not possible, look for the audio tours to get away mentally even if that is not physically possible. Also remember that under 26 get in free on some weekends and that some events in the evenings allow access to the rest of the Louvre for a few hours.

Simply incredible. The museum is HUGE, be prepared to spend all day just to cover a portion of it! We went for about 5 hours and were only able to get through about 85% of ONE LEVEL! There are 3 or 4 levels total I believe. However, everything we saw was so amazing and well worth it! I suggest buying advance tickets to skip the line, takes maybe 5 minutes to enter that way.