High in the rugged Siskiyou Mountains, a clear mountain stream cascades through a narrow canyon, and here stands one of southern Oregon's oldest attractions. Known as the marble halls of Oregon and first discovered in 1874, the caves, which stretch for 3 miles under the mountain, were formed by water seeping through marble bedrock. The slight acidity of the water dissolves the marble, which is later redeposited as beautiful stalactites, stalagmites, draperies, soda straws, columns, and flowstone. Guided tours of the caves take about 1 1/2 hours, and aboveground there are several miles of hiking trails that start near the cave entrance. Bear in mind that children under 42 inches tall are not allowed on tours. In summer, candlelight tours and "off-trail" tours are given, essentially as introductions to spelunking. To reach the monument, take Ore. 46 out of Cave Junction and follow the signs.