Montalban Gorge. Photo by Danny M, TripAdvisor website

Outdoor activities, such as trekking or camping under a canopy of stars in the mountains, are tourism activities enjoyed by people these days as being outside enjoying nature has been considered a “safer” activity during the pandemic.  

In relation to this, you might be enjoying a breezy morning in a mountain destination that belongs to sites in the Philippines declared as National Geological Monuments (NGM) by the National Committee on Geological Sciences (NCGS).

By the way, NGM is an organization established to ensure the protection and preservation of the geological structures in the country with high scientific, education, or aesthetic value. They are also tasked to promote awareness of geology among the public.

There are currently six NGM sites: 

Montalban Gorge, which was declared an NGM site in 1983, is a limestone formation in Rodriguez, Rizal. The limestone formation is produced by the build-up of remains of marine organisms in warm shallow seas 25 million years ago at the eastern edge of the Central Luzon Basin. Active forces within the earth raised and exposed the rock formation to the nonstop passage of water along cracks of the limestone body. It is considered an important site for the studies of geological processes. 

Taal Lake in 2015. Photo by Raquel P. Gomez

Declared an NGM site in 1985, Taal Volcano located in the province of Batangas is considered one of the world’s lowest and deadliest volcanoes. Surrounded by a freshwater body (Taal Lake), it is a rare example of a volcano rising out within a large volcanic depression. This volcano doesn’t have just one but several vents or cones that have changed over time.

Chocolate Hills

Chocolate Hills, declared an NGM site in 1988, is considered a major geologic feature of the Philippines. It was formed when most of the islands were below a shallow sea some two million years ago. During that time, the deposition of remains of marine organisms and the formation of coral reefs transpired. The land was later uplifted and eroded, forming valleys until isolated hills or haystack-like mounds were formed.

Image credit: CC BY-NC-ND 2.0 (Ilocos Norte, 2010)

Ilocos Norte Sand Dunes, declared in 1993, were formed a few thousand years ago through the combined action of wind, waves, and shore currents. The dunes stretch for at least 40 kilometers and cover an area of about 85 square kilometers.

Image credit:

Declared in 2001, Hundred Islands in Alaminos, Pangasinan, belonged to a massive ancient coral reef. Totaling to 124 islands at low tide and 123 islands at high tide, the islands are scattered in an area covering about 17 square kilometers. Due to the eroding action of ocean waves, some of the islands show unusual mushroom/umbrella-like shapes. 

Image credit: By Ron Van Oers – This place is a UNESCO World Heritage Site, listed asPuerto-Princesa Subterranean River National Park., CC BY-SA 3.0 igo,

St. Paul Limestone Formation is located in the Puerto Princesa Subterranean River National Park. It was declared an NGM site in 2003. This limestone formation features a spectacular karst landscape and a more than 8-kilometer long underground river known as the Subterranean River or St Paul Cave which flows directly into the sea. St Paul Cave is very impressive, with huge passages and formations of stalactites and stalagmites, and several large chambers. Its biggest chamber is 120 m wide and 60 m high.