Ancient China's Yangguan Pass in northwest China

The photo taken in March 2017 shows the Yangguan scenic spot in northwest China's Gansu Province. Yangguan, or Yangguan Pass, was fortified by Emperor Wu of the Western Han Dynasty around 120 BC. Historically, it was used as an outpost to defend enemies and was a vital pass along the ancient Silk Road. [Photo: Chinanews.com]