But seriously, they climb it then descend in one direction on the stage from Bagnères-de-Luchon to Pau, take a rest day, then climb it again from a different direction from Pau to a summit finish on Col du Tourmalet.
I did a training camp in the Pyrenees this summer and did a lot of the famous climbs. 5 HC ones including the Tourmalet. It’s a monster. A real beast. Utmost respect for the pro riders.