This is a very expensive cable car ride, but it takes you first to a half-way station and then (via smaller cable car) to 12600ft.
The views of Mont Blanc and the Chamonix valley are spectacular, and with the sun out in August, and literally freezing temperatures, it was somehow warm enough to get away with a T-shirt and thin top on.
Be aware that people book a slot on the first cable car days in advance, and without this, you have to queue up for a time-slot later in the day. This applies from 8am but you can (if you can’t sleep) catch it without a ticket (but still paying) from 6:30 to 8am.
We arrived around 9am and were given a slot of 10:30 so went to have a walk around town in the meantime.
At the top, there are 2 other things to do.
There is an elevator up to a lookout, which had a 20 minute wait time, and another cable car that takes you across a hanging valley of snow. This, however, is another (approx) €30 per person, and has another 20 minute wait.