High up in the Xishuangbanna (西双版纳) mountains, where the air is crisp and cool, a unique variety of Camellia Sinensis grows. Here, for over 1,500 years, local farmers have been harvesting the large, soft leaves of the ancient tea trees and compressing them into a cake-like casing, ready to sell to a tea market thirsty for one of the world’s finest brews. But unlike other teas, this one won’t be consumed for many, many years. For this is Pu’er (普洱) — the prized tea that, much like a fine wine, improves with age.

In contrast to the “fresh is best” rule for most teas, Pu’er — also known as the “living tea” — undergoes secondary oxidization and fermentation caused by active microbes living in the tea. Like a fine wine, Pu’er has particular vintages sought after by tea connoisseurs — “1990 and 1995 are good years,” says an assistant at the Tenfu tea shop (天府茗茶) in Wangfujing, Beijing. Originating from Yunnan Province, the “birthplace of tea” according to some anthropologists, particular areas in the province are also noted for their excellence. During the Three Kingdoms period (220-280), the great Sichuan strategist and Yunnan “Tea God,” Zhuge Liang (诸葛亮, 181–234), designated six mountains in the Xishuangbanna region as the finest for growing Pu’er, bestowing on them the informative, though somewhat unimaginative, title of The Six Great Tea Mountains (六大茶山 liù dà cháshān).

Like the Château Cheval Blanc of the tea world, Pu’er commands a high premium in the tea market, where half a kilo can cost up to RMB50,000, says the assistant at Tenfu. As a result, it’s a beverage goldmine for investors, lured in by its quality, the low supply and high demand tendency, and its ability to appreciate with age. In 2003, speculators in Hong Kong and Guangdong triggered a boom by buying large amounts of Pu’er to restrict its supply and push up the price. By the mid-1990′s it had reached a peak, with a tide of workshops, tea merchants and factories opening across China. Yet it also meant the market was flooded with Pu’er imitations, a problem that persists today. Pu’er’s price elasticity was demonstrated in 2007 when an earthquake caused heavy damage to tea factories in Yunnan. It sent tremors through the industry, with the price of Pu’er in Beijing’s Maliandao Tea Street (马连道茶叶街) rocketing by 30 to 50 percent. Speaking to China Daily, Professor Yang Sizhong from Yunnan University warned, “The price of Pu’er teas has risen too far from its actual value as a result of hype from business and investors.”

Compressed Pu’er tea dates back several centuries, to a time when merchants needed a tea that didn’t spoil along the long, arduous merchant routes. Various fermentation techniques evolved and the compressed tea was transported from Yunnan across the rough terrain of The Ancient Tea Route (茶马古道 chá mǎ gǔdào), which was considered to be the second Silk Road.

“The secrets for processing Pu’er tea are carefully guarded. It is said that, in the past, trespassers mistaken as spies have been known to be killed on private tea plantations,” according to Varat Phong, founder of the Pu’er Cha (Pu’er Tea) website. The threat has not been strong enough to repel scientists eager to discover more, though. In 2005, Yunnan Agricultural University opened the world’s first Pu’er tea college, aiming to teach future Pu’er experts and support further research. What fascinates scientists in particular is the health benefits associated with Pu’er, also known as the “wonder tonic” and “medicinal tea.” Though all species of tea contain polyphenolic compounds, offering medicinal and restorative qualities, the broadleaf variety of Pu’er also promotes microbial activity. This suppresses fatty acid synthesis and helps prevent cardiovascular diseases, making the tea particularly popular with neighboring provinces, like Guangdong, who had fatty, oily diets. High-profile celebrities, including Victoria Beckham, have even been endorsing the tea as a weight loss aide. Perhaps more groundbreaking are the results from 10 years’ worth of research by professors Liang Mingda and Hu Meijing, who find Pu’er has a statistically significant anti-cancer effect.While it has incentives for investors and health nuts, what attracts the true tea connoisseurs? For many, it’s the beguiling flavor. Phong describes the taste as both compelling and at times uncompromising, with flavors ranging from light and floral to harsh peat, leather and tobacco.

“Black Pu’er has an imposing aroma of heavy earth that is comparable to the sweet fragrance of mineral deposits emerging from deep within the forest floor after a heavy downpour,” he explains on his website. “Good Pu’er tea has excellent clarity and clean flavors that is warming to both the body and soul.” Yet, for Westerners interested in sampling the tea, it’s not easy. Aside from the high prices, the tea’s limited supply makes pure unadulterated Pu’er difficult to come by outside of Southeast Asia. A trip to one of the numerous tea markets in China is your best bet. Or, for the more adventurous tea lover, hike up the Xishuangbanna mountains to source your own. Though, if Phong is to be believed, make sure you’re not mistaken for a spy.