Las Posadas is a traditional celebration held mostly in Mexico and Guatemala during the evenings of the nine days before Christmas. It depicts a short pilgrimage that re-enacts the Christmas Eve journey of Mary and Joseph, although it started as a Mexican-Indian fiesta that was "adopted" by the invading Spanish conquistadors. Each year from Dec. 16-24, neighborhoods all over Latin America host processions, with a different house hosting festivities each night. Los Angeles has a version of the celebration on its Olvera Street that the public can participate in. Processions start at the Avila Adobe at 7:30 p.m.; local merchant families create candlelit processions of Mary and Joseph followed by children, adults and animals.