From A Wiki of Ice and Fire
and the location of the Prince's Pass
The Prince's Pass is one of the principal overland routes from the Stormlands to Dorne. It is located in the Red Mountains of Dorne.
The Prince's Pass descends from the mountains into the deep sands of Dorne. The head of House Fowler acts as Warden of the Prince's Pass.
The Winds of Winter
Two Dornish hosts have massed in the Boneway and the Prince's Pass. The hosts sit encamped, sharpening their spears, polishing their armor, dicing, drinking, and quarreling. They are waiting for the Prince of Dorne to loose them on the enemies of House Martell. 
References and Notes