Complex sentence: The name of the prison comes from the extremely boiling volcanic lake that surrounds the prison; a two-way gondola cable car system is the only way to the volcanic rim, even then one needs the use of a flying gondola to leave the island outright.
Split into simpler sentences: The name of the prison comes from the boiling volcanic lake that surrounds the prison; a two-way gondola cable car system is the only way to the volcanic rim. Even then, one needs the use of a flying gondola to leave the island outright.