Complex sentence: At the southern edge of the town the River Wye has carved an extensive limestone cavern, known as Poole's Cavern, whose more than 300 metres of chambers are open to the public.
Split into simpler sentences: At the southern edge of the town the River Wye has carved an extensive limestone cavern, known as Poole's Cavern. More than 300 metres of its chambers are open to the public.