I did this sketch long ago. It depicts an entrance to a "magma cave" (it could be that labyrinth you are talking about, Crush).

--Pajarico 18:43, 5 September 2007 (CEST)

Hexagonal basalt structures: http://centripetalnotion.com/2007/07/21/20:50:54/

Turns out looking at that page the isle in question is the Isle of Staffa, there is some "concept art" already made by Thomas Pennant in 1772. http://en.wikipedia.org/wiki/Image:Staffa_engraving.jpg