Las Ventanas is a double arch located above a meander on the lower Mascun Canyon close of the "Fuente del Mascun" (springs). The "Dolphin" nikename comes from the shape of the span taken on the north side of the arch. The largest opening (The Dolphin) has 18.5 meters span and the second opening has 13 meters. The lower Mascun Canyon is an outstanding area of rock sculpture (like "La Cuidadela") and a pleasant walk along the river to the "Oscuros de Otin", the final slot of the canyoneering trip.

How to reach : From the village of "Bierge", take road HU-341 for 18km to the hamlet of "Rodellar" (Road terminus). Park at the designated area. From the center of the hamlet, take the signed trail which lead in less than 15 minutes to the canyon floor. Walk upstream the canyon along the river (several fords) 1km to the Fuente del Mascun (springs). The double arch is located above. Two photos below shown the beautiful arch.