Less than 5 percent of the landscape is devoted to commercial and residential development, leaving the vast majority of land divided between agriculture and conservation. So it's not surprising to turn off a highway and find yourself suddenly shaded by a canopy of eucalyptus trees. The gateway to the Koloa/Poipu area provides such an experience. Long called the Tree Tunnel, this delightful stretch of Maluhia Road is just past the six-mile marker off Kaumualii Highway. The trees were first planted a century ago when they were donated to the county by a resident. Two hurricanes have taken their toll, but like all of Kauai's exuberant plant kingdom, the Tree Tunnel still thrives.