Yes, it has live jazz. Yes, it serves up tasty cocktails. Yes, it has a statue of Ceres in the corner. But you're not heading to the Green Mill Cocktail Lounge for any of that. You're heading there because of its history. Opened in 1907, the Green Mill was a favorite hangout for Al Capone and his henchmen, thanks to its dark atmosphere, and, legend has it, a series of tunnels underneath the joint that gave them a way to slip out of the bar unnoticed should the Feds stop in. You can even sit in Capone's favorite booth — with views of both entrances — but, unfortunately, the tunnels are off limits.