1. Grotto Azzurra, Italy
Grotto Azzurra or Blue Grotto is one of Capri island’s greatest attractions. It’s a sapphire-hued sea cave only accessible during low tide as the cave’s entrance is a mere metre high and two metres wide. Though not as long or as deep as many of the other caves listed here, its sheer beauty would make it worth the trip. Tours of the Blue Grotto are provided by local operators, two of which, Motoscafisti di Capri and Laser Capri, offer round-trip boat excursions from €15 (US$18). It can get a bit crowded, especially during the summer peak season. If you’d rather avoid the crowds, visit during off-peak seasons.
2. Škocjan Cave, Slovenia
This impressive Slovenian cave system was inscribed a UNESCO World Heritage Site in 1986. Containing evidence of human inhabitation as far back as 10,000 years, the Škocjan Caves are a must-see attraction for anyone travelling through Slovenia. Some of the caves’ highlights include one of the world’s largest known underground canyons; the Big Collapse Doline (or sinkhole) and the Little Collapse Doline, where the entrance to the caves can be found; the Rimstone Pools and even some underground waterfalls.
3. Waitomo Glowworm Cave, New Zealand
Famous for being home to a species of glowworm endemic to New Zealand, the Waitomo Glowworm Caves of North Island offer visitors a jaw-dropping encounter with one of Mother Nature’s true wonders – the shimmering bioluminescence of these special insects.
A number of cave tours are available, with the Waitomo Glowworm Cave Tour (NZ$50 or US$36) taking spelunkers through the renowned Glowworm Grotto. In addition to touring the vast cave systems at Waitomo, several other adventure activities are on offer, including rock climbing, blackwater rafting and abseiling.
4. Sterkfontein Caves, South Africa
Located about a 45-minute drive from Johannesburg, the Sterkfontein Caves are notable, particularly in the discipline of paleo-anthropology. Not only are the caves beautiful and boast an impressive underwater lake, but due to the vast number of fossils recovered in the area, the region in which the caves are located has been dubbed the Cradle of Humankind, and has been granted UNESCO World Heritage status.
The caves are open to the public every day from 9am to 5pm with tours costing R165 (US$13) for adults. If you have the time and inclination, go for a combo ticket (R190) which gives you access to both the caves and the incredible Maropeng, the Cradle of Humankind’s award-winning visitors’ centre and interactive museum.
5. Cango Caves, South Africa
Another impressive South African cave system, the Cango Caves outside of Oudtshoorn in the Western Cape are a real natural phenomenon. Famed for their spectacular, almost otherworldly speleothems (cave formations), the caves attract visitors from all over the world. Two tour options are available for visitors: the 60-minute Heritage Tour (R110) and the 90-minute Adventure Tour (R165) respectively.
To preserve the cave’s integrity, limited numbers of tourists are permitted each day, so booking in advance is essential. Additionally, due to the cramped and often tight spaces within the cave systems, pregnant women and those suffering from claustrophobia, high blood pressure or muscular ailments are advised not to visit.