The granddaddy-or should we say grandma?-of dinosaurs is Sue, the Field Museum's poster girl. The 67-million-year-old skeleton is the largest, most complete and best preserved T. rex that's ever been found and includes a whopping 224 bones. Her original skull is kept in a separate case-although at 600 pounds, or about the size of a cow, it's a bit hard to miss. Fun fact: Sue's got a Twitter account! Follow her @SuetheTRex. The Field's Genius Hall of Dinosaurs also highlights a few less famous dinos, such as Rapetosaurus krausei. If you're longing for a 'saur sleepover, watch for the Field's "Dozin' with the Dinos" overnights, where a premium ticket snags you a spot in the middle of the hall. Our advice: keep one eye open, in case of some Night at the Museum-style high jinks.