Caves are eerily mysterious--you never know what you might discover inside. These naturally made formations are some of the most wonderful sights ever, and around the world, there are plenty of them that are open for exploration.

But there are caves too that don't seem daunting at the least. They are beautiful and inviting and seem like the stuff out of your favorite storybooks. Here are some of the most amazing caves in the world that you can visit. 

Puerto Princesa Underground River, Palawan, Philippines. One of the new 7 wonders of nature, it's impossible not to include this on the list. This beautiful cave is full of wonderful stalactite and stalagmite formations. It's a popular tourist attraction in the Philippines and even though it's the longest navigable underground river in the world, the deeper part of the cave cannot be explored due to oxygen deprivation.

Onondaga Cave, Missouri, USA. Now protected as part of the Missouri National Park, Onondaga Cave is a beautiful phenomenon in which visitors can do a number of fun activities inside such as swimming, cave tours, hiking, and fishing. It's full of dripping stalagmites and active flowstones, and the water inside the cave seems to radiate an eerie glow.

The Blue Grotto, Capri, Italy. A famous tourist attraction in Capri, it always draws visitors all year-round because of its unique emerald glow. The whole atmosphere inside the is emerald blue, because of a small opening inside the cave in the entrance and another hole beneath the water line in the entrance. When the holes reflect the sunlight inside the cave, it gives off a beautiful blue color.

Eisriesenwelt Ice Caves, Werfern, Austria. The largest ice cave in the world, this beautiful natural phenomenon is located inside the Hochkogel Mountain, a Tennengebirge section of the Alps. More and more tourists visit this cave every year because of the ice formations inside the cave, which is made of natural limestone ice.