Literally, the "sea of ice," the Mer de Glace glacier can be seen up close from the Train du Montenvers, a cogwheel mountain train that leaves from behind the main train station. At the top end of the track you can mount yet another transportation device—a mini-téléphérique (cable car) that suspends you over the glacier for five minutes. You can also venture into the grotte de glace (ice cave). The hike back down is an easy two-hour ramble.
Chamonix, 74000, France