Uncut, pristine, and a mere 6 kilometers (3.7 miles) from a major city center, Penang Hill defies the commonly held notion of what and where a rainforest should be. It’s neither hard to reach, nor particularly gritty, with an immaculate train providing access and cafés serving visitors who make the 15-minute journey from George Town. And yet, this vast patch of old-growth tropical hardwoods, stretching across some 8,000 hectares (19,768 acres) on Malaysia’s island state of Penang, is home to astounding—and untold—biodiversity.

Pristine forest is becoming increasingly rare throughout most of the world, not least in Southeast Asia, where rainforests continue to be slashed to meet the demand for timber and lucrative cash crops like palm oil. The rainforest of Penang Hill, first protected in 1911, stands as a valuable living time capsule 130 million years in the making, and scientists and conservationists aim to keep it that way. Earlier this year, the Universiti Sains Malaysia and the California Academy of Sciences assembled a team of 117 biologists from nearly a dozen institutions to conduct a comprehensive biodiversity survey of the forest. The researchers hope that their findings—more than 1,400 species of plants and animals, including at least four species that are likely new to science—will contribute to a successful nomination of the rainforest as a UNESCO biosphere reserve. These images capture just a few of the highlights from an intensive effort that the international team hopes will not only further scientific understanding but also help to ensure the long-term preservation of this rare jewel on the Malay Peninsula.