Complex sentence: The only cliff woodland of the Lizard Peninsula is at the Devil's Frying Pan, an old collapsed sea cave, which contains Cornish Elm, Dutch Elm and an intermediate variety of elm.
Split into simpler sentences: The only cliff woodland of the Lizard Peninsula is in the locality of the Devil's Frying Pan, an old collapsed sea cave. This woodland contains Cornish Elm, Dutch Elm and an intermediate variety of elm.