The Kalalau Trail – Kauai, Hawaii, USA (17/20)

This 11-mile trail along Kauai’s Napali Coast is known for its steep, muddy, and often dangerous conditions. Frequent rain can make the trail slippery, and some sections require hikers to scale rock faces or cross streams. The trail ends at the secluded Kalalau Beach, one of the most beautiful and remote spots on the island.