It's traditional to build an altar to remember family or friends who have died for the Day of the Dead. They might have purple and yellow plastic banners, cempasuchil, candles, food, photos, and more.
Here are some altars we saw yesterday. The huge one was at the City Museum. They've been creating an altar there for years and everyone at the museum helps. The others are altars we saw as we wandered around yesterday in homes, stores, and churches.