Imagine a classic Chinese landscape of bamboo forest, rice paddies and lotus-filled waterways, dotted with villages that seem untouched by time. Now add to that scene hundreds of castle-like watchtowers, their turrets rising unexpectedly against the skyline. This is Kaiping in Guangdong province, just a couple of hours from Hong Kong by direct high-speed train from West Kowloon Station. It is one of mainland China’s lesser-known Unesco World Heritage sites and home to more than 1,800 distinctive...