Want a unique way to explore Kauai’s emerald-green interior? Try mountain tubing with Kauai Backcountry Adventures, based in Lihue. Here, you sit on an inner-tube and float down the canals and tunnels that formed the Hanamaulu ditch system, which was engineered and hand-dug in 1870 to irrigate the former Lihue Sugar Plantation. The waterways run through some of the most beautiful and remote land on the island with spectacular mountain views.  It’s suitable for those in generally good physical shape, aged five and over.