Complex sentence: In 2001, a house foundation and a underground water pipe system dated to Song Dynasty were discovered in Mong Tseng Wai of Yuen Long, the only Song Dynasty village site in Hong Kong.
Split into simpler sentences: In 2001, a house structure with underground water system dated to Song Dynasty were discovered in Mong Tseng Wai of Yuen Long. It was the only Song Dynasty village site in Hong Kong.