The cave – there's only one – contains about 3 miles of passages, explored via 90-minute walking tours that expose visitors to dripping chambers and 520 rocky steps. The trail, which requires ducking at times, follows an underground waterway called the River Styx. Guided tours (the only way to access the cave) run at least hourly, half-hourly in July and August.
Dress warmly, wear good shoes and be prepared to get dripped on. For safety reasons, children less than 42in (106cm) tall are not allowed on tours. In peak summer months, waiting times for a tour might be an hour or more. Definitely reserve online.
