The Piedra Herrada Butterfly Sanctuary near Valle de Bravo in the State of Mexico is a brief home to millions of monarch butterflies every autumn. Monarch migration takes around eight months, and during that time four consecutive generations of butterflies are born and die.

The final generation makes it back to the Sanctuary every autumn and begins the migration again in the spring.

At the Sanctuary, it’s easy to see the butterflies blanketing trees and swarming overhead. From a distance, the clusters look like beehives. But if you get up close, you can observe their natural beauty.

Every day around midday, the butterflies descend from the mountain to drink from a nearby natural spring that serves as their watering hole.

To get to the butterflies, you can hike to the reserve’s main observation point, which takes about 45 minutes along dirt paths. But you can also view the butterflies from the comfort of your vehicle. Piedra Herrada has one of the most scenic drives in the world, and you can watch the journey up and down the mountain while taking in the view.

Tune into The Travel Detective with Peter Greenberg each week on public television to watch more of Peter’s Hidden Gem adventures.