It probably sounds nerdy, but one of my favorite things to do in Berlin is visit the Loxx Miniature Railway system. The 3,000 square meter model of Berlin is full of incredible details - some real, and some improvements on the real city. Its attention to detail and its sense of humor are amazing - it features everything inside Berlin's Ringbahn (the circular subway that surrounds the inner core of Berlin). It includes an airport with planes that take off and land, a traditional Christmas Market with a drunk Santa, a Tina Turner concert, and naked sunbathers. Take a tour of this miniature version of Berlin. It's almost as fun as visiting the real Berlin.