Red Rock Coulee

Scattered across a coulee in southeastern Alberta are hundreds of round red boulders, some of them two and a half metres across, among the largest concretions in the world. They formed inside the surrounding sandstone: mineral-rich water precipitated cement around a nucleus, building outward in a sphere, and as the softer rock around eroded away the harder balls were left sitting on the surface. The iron oxide gives the colour. The coulee is dry short-grass prairie with cactus, rattlesnakes and scorpions, and it is one of the hottest and driest corners of Canada. There are no facilities beyond a small parking area and an interpretive sign.

What you actually see

• The stone spheres - concretions up to two and a half metres across.
• The formation process - broken examples showing the layered interior.
• The short-grass prairie - cactus, sage and a genuinely arid landscape.
• The open horizon - one of the emptiest viewpoints in southern Alberta.

When to go

May to September, with morning and evening light strongest on the red rock; midday summer heat is extreme with no shade at all. Spring brings cactus flowers.

Honest expectations

Prairie rattlesnakes are present and the ground is uneven. There is no shade, water or facilities. The access road is gravel and becomes impassable clay in rain.

Nearby

Medicine Hat lies north; the Cypress Hills are east.