[Photo provided to chinadaily.com.cn]

What's huge and solid stone and about 380 million years old?

You may not know if you haven't been to Zhangjiajie in Hunan province, but local officials there are eager to spread the word about Yangjiajie and its stunning peak walls carved from mountains by nature over the millennia.

Part of the UNESCO World Heritage Site Wulingyuan Scenic and Historic Interest Area, Yangjiajie boasts about a dozen of the immense parallel walls of varying heights. Ongoing tourism development projects will be completed in March, local tourism officials said at a recent press conference at Diaoyutai State Guesthouse in Beijing.

"The peak walls are an integral part of the Zhangjiajie's landscape. A single stone wall is not uncommon in sandstone areas, but it's very rare that a group of such pretty and lofty stone walls maintain intact after all these years," says Chen Anze, a researcher from Chinese Academy of Geological Sciences, who visited Yangjiajie in December to investigate the landscape of the peak walls.

Zhangjiajie gained international fame when the Hollywood blockbuster Avatar in 2009 drew inspiration from its splendid mountains and pillar-like formations.

The descendants of generals of the Yang Family, who sacrificed themselves to defend their country from foreign invasion in the early Song Dynasty (960-1279), moved and settled in Yangjiajie many years ago. That's why the place got its name, and many scenic spots also have names related to the family to memorialize their ancestors.

Related: Magnificent peak walls in Yangjiajie