Ages 10 & up
Near Angangueo & Ocampo, Mexico

High in the mountains of northeast Michoacán, you're hiking up a mountain, no doubt fighting for breath in this altitude.

Then you arrive in a grove of fir trees -- and whatever breath you had left is truly snatched away. The branches on all sides sway under the weight of butterflies, massed millions of monarch butterflies with fluttering gossamer wings.

The monarchs have been coming here since time immemorial; the ancient Aztecs revered these poisonous black-and-orange butterflies, which they believed were the reborn spirits of fallen warriors, dressed in battle colors. There are actually seven monarch nesting grounds in Michoacán (nesting season lasts from mid-Nov to Mar). Only two, however, are open to the public: El Rosario and Chincua, both reachable by day trip from the graceful Colonial-era city of Morelia, which is about halfway between Mexico City and Guadalajara.

Save the trip for a sunny day if you can -- the effect is most dazzling with the benefit of a little sunshine.

It is possible for you to visit the sanctuaries on your own, but a licensed English-speaking guide is a worthwhile investment -- they can answer the kids' scientific questions, transport you reliably over the back roads to the sanctuary, and steer you right to the nucleus of the butterfly colony, which constantly shifts around the mountain throughout the season. Guided butterfly excursions take 10 to 12 hours and usually provide lunch. While it varies, the hike through the mountain forest will probably take around an hour each way; it's often a steep walk, so wear sturdy shoes. One option at Chincua is to ride up on horseback; a local handler will lead the horse for you (facilities for renting are at the sanctuary gate). English-speaking guides can be contacted through a cooperative called Mex Mich Guías (www.mmg.com.mx).

Information: Michoacán Travel (www.michoacan-travel.com).

Nearest Airport: Morelia.

Accommodations: Best Western Hotel Casino, Portal Hidalgo 229, Morelia (tel. 52/443/3131-328; www.hotelcasino.com.mx). Villa Montana, Patzimba 201, Col. Vista Bella, Morelia (tel. 52/443/314-0231; www.villamontana.com.mx).