Pioneers Thought This Idaho Landscape Looked Like a Ruined City

If you drive near the Utah-Idaho border, the flat sagebrush suddenly turns into a giant, ruined city made entirely of stone.

This is the City of Rocks National Reserve. There are no actual buildings here. It is just hundreds of massive granite spires, domes, and fins shooting straight up from the dirt.

The California Trail pioneers walked through this exact spot in the mid-1800s. They were exhausted from months of travel, but the landscape totally surprised them. They wrote in their journals that it looked like a ruined city with steeples, houses, and streets. You can actually still see their names written on the rocks in wagon axle grease.

Magma Cooled Underground

To understand how this stone city formed, you have to look deep under the earth. About 28 million years ago, a massive pool of liquid magma pushed up into the crust. But it never erupted like a volcano. Instead, it got stuck underground.

Over a long period, that magma slowly cooled and hardened into solid granite. As it cooled, the massive rock block contracted and cracked.

The geology here is strange because it is a mix of two entirely different rock ages. Some of the granite is about 28 million years old. But right next to it, you can find dark, twisted rock that is over 2.5 billion years old. That makes it some of the oldest exposed rock on the entire North American continent.

The Dirt Washes Away

For millions of years, this solid granite just sat buried in the dirt. But the Earth’s crust shifted. The ground pushed upward, and the soil on top slowly washed away.

Eventually, the hidden granite was exposed to the open air. Because the rock was already full of deep vertical cracks, water seeped right in. When water freezes, it expands. It acts like a wedge, snapping off pieces of the stone. Wind and rain helped finish the job. They eroded the sharp edges of the broken granite, leaving behind smooth, towering pillars.

People travel from all over the world to rock climb here. The rough granite gives them plenty of grips. It is a strange, quiet place that really does feel like walking through an empty city made entirely of stone.