Experiencing a much larger version of something than normal makes you realize what you've been missing, as when you see an IMAX film after a regular movie or move into a castle after living in a dollhouse. Go big with today's Groupon: for $18, you get four documentary movie tickets to the Select Medical IMAX Theater at the Whitaker Center (up to a $38 value) on Market Street.

The Whitaker Center's Select Medical IMAX Theater dazzles moviegoers with 3-D adventures projected onto a six-story screen and piped through a six-channel, 16,000-watt surround-sound system. The 65' x 80' screen towers over the audience, immersing them in overwhelming three-dimensional visuals like a diorama built in Paul Bunyan's shoebox. Swing from the trees with Born to be Wild 3D, a heartwarming documentary narrated by Morgan Freeman that introduces audiences to the lives of orphaned orangutans and elephants and their human care-givers. Hubble 3D follows the crewmembers of the space shuttle Atlantis on their mission to repair the Hubble Telescope, giving viewers a close-up look at such breathtaking galactic events as the birth of stars and the Quinceañera of planets. Check out the showtimes for all current films.