From above, it's just a crack in the ground. Climb down inside and the walls swirl around you in waves of orange, red and purple.

Antelope Canyon is a slot canyon on Navajo land near Page, Arizona. Over vast stretches of time, flash floods have carved the soft Navajo Sandstone, smoothing it into these flowing curves. The sandstone itself formed from ancient desert sand dunes.

Around midday in summer, beams of sunlight can shine straight down into the canyon, lighting up floating dust like searchlights.

It's beautiful but dangerous. Rain miles away can send a flood roaring through with little warning, and in 1997, eleven people died when a flash flood swept through Lower Antelope Canyon. Today it can only be visited with a Navajo guide.