I love the Bellagio fountains. They do an incredible job timing music to fountains, and it is a different music/show every time I go to Vegas. The area in front of the fountains starts getting crowded about fifteen minutes before the show, so be sure to go a little early and grab a spot front and center. I have watched the fountains both during the day and at night, and both have something to offer. I like to see the water glisten under the sun, and how clearly I can see the water move during the day (but it is HOT in the summer waiting for the show to start). At night, I love the lights and the romantic feel to the show. All-in-all, this is one of the best free things to do in Vegas, and the fountains are a Vegas icon. You have to see it once during the day and once at night.