The celebratory customs associated in various countries with Christmas have a mix of pre-Christian, Christian, and secular themes and origins. Popular modern customs of the holiday include gift giving; completing an Advent calendar or Advent wreath; Christmas music and caroling; viewing a Nativity play; an exchange of Christmas cards; church services; a special meal; and the display of various Christmas decorations, including Christmas trees, Christmas lights, nativity scenes, garlands, wreaths, mistletoe, and holly.