Without a doubt, the Col de la Piedra de Saint Martin or Pierre Saint-Martin is one of the Top 10 in the whole of the Pyrenees. Without exceeding 2000 metres of altitude, it is a very long pass, with a lot of accumulated gradient (due to the innumerable French slopes, the gradient is 1,450 metres), with very hard slopes and several kilometres above 10%, with wonderful landscapes and panoramic views and with little traffic, except for the slopes crossed by the main road (D132 in France, the NA 137 in Spain).
It is a pass with many slopes; in Europe there are few other passes that have as many slopes as this one (col de Turini, Passo delle Erbe, would be comparable in number of slopes approximately).
I have only climbed it by 2 slopes: (i) my first time was from Lourdios Ichère, crossing the col de Labays and the col de Soudet. Simply spectacular; (ii) I have subsequently climbed the Spanish side on several occasions, which is unique, and which starts from Belagua and crosses the Belagua cross-country ski resort to reach the mountain pass. It is also very beautiful, with a landscape and views different from the north-east side. If I had to choose one of the two, I liked the north-west side better because it is more remote, harder and in my opinion more authentic.
It is also a culturally special mountain pass because the Tribute of the 3 cows takes place on its summit every 13th of July, which is considered the oldest treaty in force in Europe.
So... you know... you cannot miss the opportunity to come here and enjoy this wonderful jewel of the Pyrenees!!!!