The Caves of Arta (Cuevas de Artá or Coves de Arta among the locals) are located on the eastern part of Mallorca, next to the sea, south of local village Artá, near Playa de Canyamel on the Cap Vermell.
Among the local caves visited, it was the only one not expressly forbidding photography, so I shot happily away, but with no tripod quite a few of the shots had to be discarded (any shots taken with flash obviously didn't capture the whole "spooky" athmosphere created by well-places lighting (as well as ruining fellow visitors' eyesight ;-)
Photo shot handheld using my Canon EOS 10D, ISO 800, Shutter 1/8s, lens: 20-40mm at aperture f/2.8