Guadalupe Day in Mexico

DEC 12: Day of the Virgin of Guadalupe (Fiesta de la Virgen de Guadalupe) — Nationwide. The most important holiday in Mexico in which millions of pilgrims converge on the Mexico City Basilica of the country’s patron saint to pay tribute. The square in front of the Basilica is a stage for singing, dancing and celebration.

http://www.sancta.org/basilica.html