Chocolate Hills: The color-changing mounds in the Philippines that inspired legends of mud-slinging giants

The Chocolate Hills are a formation made of 1,776 limestone, grass-covered mounds in the Philippines.

This landscape is lush green during the rainy season from February to May, but in the dry season, the hills turn cocoa brown, giving the formation its name.

The Chocolate Hills were designated a national geological monument of the Philippines in 1988 and were granted protection as a natural monument in 1997. There is no other formation quite like them in the world, with just one region in Java, Indonesia, having a similar, but less impressive geology.

The hills are between 100 and 390 feet (30 to 120 meters) tall and have tapering tops. They are examples of what geologists call "mogotes" — steep-sided mounds that occur in tropical karst landscapes, or areas that have a soluble bedrock and host sinkholes and cave systems. Numerous underground caverns and springs have been documented around the Chocolate Hills, according to a 2001 research article, with some caves potentially existing directly beneath the mogotes themselves.

Evidence suggests the Chocolate Hills formed sometime at the start of, or just before, the last ice age (2.6 million to 11,700 years ago), when tectonic processes lifted coral and other marine deposits. These deposits were then exposed to rainfall and erosion, which carved the landscape into regular mounds.

Local myths have tried to explain how the Chocolate Hills formed. According to one legend, the mounds formed after a mud-throwing fight between two giants. Another tale says the region was once inhabited by giant children, who, while competing to make the most mud cakes, baked them under coconut half shells that eventually became the Chocolate Hills.

The land between the hills is flat and cultivated with rice and other crops. When the Chocolate Hills were declared a natural monument in the late 1990s, farmers, small-scale miners and landowners rose up against the government because they feared environmental protections would curb their property rights and livelihoods.

These protests escalated into violent conflicts between the military and a guerilla group dubbed the "Chocolate Hills Command," according to the 2001 article. Two armed fights broke out, one of which caused 10 deaths in October 1999.

Balancing the diverse and sometimes conflicting needs of environmental protection, tourism and local residents still poses a challenge today; the construction of a resort in the middle of the Chocolate Hills sparked public outcry in 2024.

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