Water pressure in the 200-foot lava tube is so great that spray sputters out from cracks in the cave roof. The secret behind the river's disappearing act at Natural Bridge is a lava tube. Several thousand years ago Crater Lake's volcano filled this canyon with a long basalt lava flow. When the lava's crusted surface stopped moving, the molten rock underneath kept on flowing, leaving long caves. At Natural Bridge the Rogue River funnels through one of these tubes like water through a hose.
Most tourists turn back here.
But a lovely, quiet portion of the Upper Rogue River Trail continues upstream. In early summer, large patches of 5-petaled white anemones bloom here beneath old Douglas firs. Also look for vanilla leaf, with three big leaves and a stalk of tiny white flowers. A mile beyond Natural Bridge take a fork to the right, cross the river on a footbridge over a churning chasm, and turn right on the Rogue Gorge Trail for 1.1 mile to return to your car. Then keep left for 0.7 mile to the Natural Bridge parking area.