Boca do Inferno is located on the west coast of the town of Cascais. The name "Boca do Inferno" (Hell's Mouth) attributed to this place is due to the morphological analogy and the tremendous and frightening impact of the waves that are felt there. The characteristic that composes the rock in the cliff is of carbonated nature. The erosion exerted by the action of rainwater which, containing dissolved carbon dioxide, causes the carbonate to dissolve. Through this process cavities and caves are formed inside the limestones.
It is quite possible that the site was an ancient cave. With the abasement of the upper layers the cave might have been destroyed, leaving an enormous cavity in the open. With unique characteristics, it is a place of leisure, where you can enjoy a divine landscape and magnificent sunsets. At present, the sea with violent and ruthless clashes, rises in white and deadly foam for tens of meters, continuing the wear on the millenarian rock, increasing in this way the spectacularity and the size of the "Boca do Inferno".
Knowing Cascais is like living in time and at all times. Magical place of the Portuguese society, it keeps testimonies of varied times of human occupation and their close relation with the Atlantic as well as with the proximity to the Portuguese capital. The seaside palaces, the stories of spies and conspirators, the signs and defenses of the coast, the streets and the citadel form a unique mosaic of the Lisbon coast. It is here that we find the most important geological evidence of karst erosion, the Boca do Inferno, where the sea and the land fight permanently in an endless duel, almost giving this place the Portuguese mysticism and value of the maritime conquest.