Geysers, blowholes and caves: the surprising tourist attractions

Strokkur, in the Haukadalur valley, is Iceland's most visited geyser because it's so reliable, with eruptions happening about every 10 minutes or so, making it ideal for tourists looking to experience Iceland's famous natural beauty.

Strokkur usually erupts to about 15 or 20 metres, but has been known to get as high as 40 metres.

Soar above the coast of Belize and you’ll glimpse the wonders of the deep, or don your scuba gear and make a beeline for Lighthouse Reef, where the Great Blue Hole lures divers into its yawning 1,000-foot-round cavern.

After the discovery of an 83-carat diamond in 1871, people rushed to South Africa to dig frantically – and deep – for more buried treasure. Today, the world’s largest man-made hole stands as a reminder of the diamond-rush days and as you peer into the 1,097-metre abyss, ponder where those three tons of diamonds may have ended up…

Yellowstone's Grand Prismatic Spring is the largest hot spring in the USA, and one of the largest in the world. First noticed by geologists in 1871, the 90m wide spring is now a popular tourist attraction.

The spring gets its magnificent colour from microbial mats around the edges of the water, and the colour changes depending on the temperature. In summer they're orange and red, while in winter they're dark green.

At Kiama Blowhole in Australia spectators may want to stand a respectful distance from this, one of the most powerful sea-cave blowholes in the world. With water spurting up to a staggering 82 feet, not only will you get soaked, you may get swept away in the Pacific surf.

Beneath the innocuous wheat fields of western Ukraine there is a vast network of caves known as the Gypsum Giant cave system. One of the entrances into this underground labyrinth is a meagre-looking opening belying the 77 miles of caverns beyond.

Travellers to the Yucatan Peninsula, Mexico, are just as drawn to the ancient Mayan site of Chichén Itzá as they are to Ik-Kil, another Mayan site where royalty once bathed in the dazzling blue water. Known as ‘cenotes’, there are thought to be thousands of these natural wells scattered along the Mexican coast.