The summer heat encourages travelers to travel to the sea coasts or to northern countries, but many wise tourists plan to visit caves during this period.

In U.S. national parks are located more than 4700 caves that will give coolness in the summer heat, writes USA Today.

Some of these caves are among the most spectacular in the world, and you should definitely find time to visit them.

Carlsbad Cave National Park, New Mexico: if you could explore only one cave in your life, you should choose this one. Of the two American caves on the UNESCO list, Carlsbad is the richest – with a huge collection of stunning formations.

Mammoth Cave National Park, Kentucky: This park has the longest cave system in the world with more than 400 miles (644 km) of explored tunnels. While touring this cave, you will not only see stunning cave formations, but also learn about strange creatures that live in these dark labyrinths.

Gem Cave, South Dakota: The third longest cave system in the world with at least 195 miles (314 km) of passages with bizarre formations such as plaster flowers, balloons with hydro-magnesite, black manganese crystals and many others. These are large calcite crystals, which were formed under water and are located on all walls and the ceiling of the now dry cave, are precious in appearance of formation.

Lava Beds, California: Over 700 caves with surreal landscapes make this park a good place to explore the caves created by volcanic activity. These winding tunnels range from relatively easy to navigate caves to real labyrinths.

National monument “Craters of the Moon”, Idaho. This volcanic wonderland gives access to four very different lava caves on one 2.6-kilometer trail. One of them is the largest Indian cave, which is well illuminated by sun rays penetrating through “light hatches”, which were formed in the ceiling. At the same time, the monument also includes a very dark cave, in which there is no way to pass without a flashlight.

Hawaii Volcano National Park, Hawaii: The forces that created the amazing Thurston Lava Tube Cave are back in business, causing the volcano to erupt in Hawaii, so new charming caves may soon emerge on the islands.

Lakes of the Apostle, Wisconsin. One of the most outstanding collections of so-called sea caves is scattered among 21 islands and along the shores of the lake. There you can see charming arches, columns and bridges made of sandstone.

National recreation zone “Golden Gate”, California: an excellent stretch of coastline with majestic sea caves. At the moment there are 82 different cave objects.

Wrangell-St. Elias National Park & Preserve, Alaska: this extreme journey will give you penetration into the terrible depths of the glacier. But be careful – such caves melt many dangers.

Mount Rainier National Park, Washington: From the 1930s to the early 1980s, the Paradise Glacier Ice Caves were one of the most popular features of this national park. Now only vivid photos and memories are left of them, as the lower part of the glacier melted due to global warming.