This special Christmas tradition begins on December 16th. The word "posadas" mean "inn" or "lodging". This festival celebrates the story of Joseph and Mary searching for an inn where Mary could give birth.
To celebrate this festival, people go door to door, knocking on doors, pretending to search for a place where Joseph and Mary can stay. They carry lanterns and sing songs, somewhat like caroling. They also carry an entire, and typically large, nativity scene.
When they reach the spot where the nativity scene will "spend the night" (by prearrangement), they have a big feast. They do this for nine nights. The route is carefully planned out.
This holiday is a wonderful reminder of the spirit of Christmas. It is also a very fun Christmas tradition.