Boca do Inferno, Hell's Mouth, located near Cascais town in Portugal is an impressive location which is quite popular amongst tourists. It's a chasm in the seaside cliff. Water having an easy access into it through some sort of gate or mouth, strikes its rocky walls with great power (it really isn't a nice place to be in I guess).
This HDR photo was in fact taken outside of the Boca do Inferno. However, you can see how angrily the waves are hitting the cliff. The mouth itself can be seen in this photo as a black square-like shape in the right side of the cliff.
As you can see it's another black & white HDR photo I've taken recently :)
BTW check out my HDR tutorial: http://hdrphotographer.blogspot.com/2012/02/hdr-photography-tutorial.html