Rosh HaNikra grottoes

Rosh HaNikra or Hanikra is a geologic formation on the border between Israel and Lebanon, located on the coast of the Mediterranean Sea, in the Western Galilee. It is a white chalk cliff face which opens up into spectacular grottos.

The Rosh HaNikra grottoes are cavernous tunnels formed by sea action on the soft chalk rock. The total length of the tunnels is about 200 meters. They branch off in various directions, with some interconnecting segments. A tunnel was built by the British for the Haifa-Beirut railroad line, and in 1968 a second one was dug, both connecting the grottoes with each other and allowing access along the former route of the British railroad.

Source: Wikipedia