Stalagmites, stalactites, flowstone deposits, and crystals entice visitors to the Lake Shasta Caverns. To see this impressive spectacle, you must take the two-hour tour, which includes a catamaran ride across the McCloud arm of Lake Shasta and a bus ride up North Grey Rocks Mountain to the cavern entrance. The caverns are 58°F year-round, making them a cool retreat on a hot summer day. The most...