After Sunday's introduction to the Pyrenees, today's stage takes us 187.5km from Pamiers to Bagneres-de-Luchon, and features the second category Col de Portet d'Aspet and Col des Ares, 100 years on from the first time that the Tour passed this way.
But the focus of attention should be on the hors category Port de Bales after 145-ish km - this beast is a 19.3km climb up to 1755m, with an average gradient of 6.1%, rising to 11% in sections, and is followed by a tricky 21km descent down to the finish line.
There are two sprints - one before the real climbing begins, and one in the valley below the Port de Bales - so there may be some duelling between Alessandro Petacchi and Thor Hushovd for some green-jersey points at the first one, but probably not the second.
Petacchi, remember, leads Hushovd by two points, and is 25 ahead of Mark Cavendish.
The main focus, of course, will be on Alberto Contador and Andy Schleck; will the Luxembourgeouis try to take time out of the Spaniard? Or more to the point, can he?
Or will Denis Menchov and Samuel Sanchez try again to pull a fast one?
I'll be doing my best to keep you up to speed, and don't forget we have up to an hour and a half of live commentary from the Radio 5 live sports extra team, starting at 1445 BST.