Hasst River gathers its water from a network of creeks and streams flowing and often cascading down the Southern Alps along Hasst Pass. The river runs 66 miles before emptying into the Tasman Sea on the west coast. Haast River Valley was formed by a series of glaciers extending back two million years. The most recent glacial period was within the last 20,000 years. This gorgeous canyon is included within the Te Wāhipounamu, registered as a UNESCO World Heritage Site in 1990.