Crater Lake, the bluest water in America.

Field guide ◆ Crater Lake

Plan the trip.

Crater Lake formed when Mount Mazama, a 12,000-foot stratovolcano in the Oregon Cascades, erupted catastrophically about 7,700 years ago and collapsed inward — leaving a 5-mile-wide caldera that filled over centuries with snowmelt and rainwater. There are no rivers in or out. The result is the deepest lake in the United States (1,943 feet) and one of the bluest bodies of water on earth — a color that's not photographic exaggeration but a function of pure water and depth.

For 2 days: Drive Rim Drive (33 miles around the caldera) on day one, stopping at every overlook. Hike the Garfield Peak trail (3.6 miles) for the best lookdown view. On day two, take the boat to Wizard Island (the volcanic cone in the lake itself) — only way to actually touch the water. Reservations required.

Best window: late July through September. The park gets 43 feet of snow annually; Rim Drive doesn't open until July most years. Mazama Village campground has reservable sites. Combine with Oregon coast or Bend for a longer Pacific Northwest trip.