Palawan, an island in the Philippines, is slowly becoming a top international destination for its world-class beaches, but did you know it's also where the longest navigable underground river is located? The Puerto Princesa Subterranean River National Park, or Puerto Princesa Underground River, is one of the new 7 Wonders of Nature.

Located about 80 kilometers (50 miles) north of the city center of Puerto Princesa, Palawan, the Puerto Princesa Subterranean River National Park is a sight to behold. Because of its recent inclusion on the list of the new 7 Wonders of Nature, tourists all over the world make it a point to include the said river on their travel bucket list.

From a 15-minute boat ride from the Sabang Wharf or a short mountain hike, you will be able to reach the Puerto Princesa Subterranean River National Park. In your tour, you, along with a small group, will ride a paddled boat with a local tour guide and explore the inside of its limestone caves with only the use of a flashlight.

The subterranean river is actually over 8 km in length, but tourists are only allowed to go 1.5 km into the cave. If you get a special permit from the Subterranean River National Park Office in Puerto Princesa, you will get a chance to travel up to 4.3 km inside the cave, but it costs more than the usual underground river tour fee.

Inside, impressive stalactite and stalagmite formations are often the highlights of the tour, with bats and other cave-dwelling animals occasionally seen inside. No loud noise is allowed during the tour so as not to disturb the ecosystem inside the cave. The local guide will point out all the features of the cave, but instead of actual geological facts they use double entendres and jokey lines which usually make tourists laugh.

An impressive natural formation, the Puerto Princesa Subterranean River National Park is a fiercely protected area. And in 1999, it was included in the UNESCO World Heritage List.

Although it's always open 365 days of the year, one some occasions tour viewings are not allowed when the weather is not particularly mild or when the seas are too rough. If you plan on visiting on a certain date, make sure to call Sabang Information Office in advance whether it is advisable to come so you won't waste your time. January-May is the best time to visit.

Several tour agencies in Palawan offer inclusive tours to the Puerto Princesa Subterranean River National Park. Aside from the cave tour itself, there are other activities you can explore in Sabang, such as treading the mountain or monkey trail or ziplining from the mountains to the beach.

So this year 2017, why not include exploring one of the 7 Wonders of Nature in your travel bucket list? You will be amazed.