Berlin
Berlin's chilly, snowy winters are ideal for indoor activities, but if you visit in December, you must also check out the Christmas markets. Glassblowers, craftsmen, carousels, and warm gingerbread combine to make for an incredible holiday experience at Potsdamer Platz's Winterworld, the historic Gendarmenmarkt Christmas market, and the Domäne Dahlem Advent market (placed at a former manor).
Visit the Botanical Garden while you're dressed for the cold, as it turns into the Berlin Christmas Garden from mid-November to early January and has its own ice rink and magical fairy lights. At any time of the year, you must also see the outdoor exhibits about Berlin Wall. Berlin's Museum Island is the place to go for indoor entertainment since it is home to five museums that house everything from sculptures and works of art to the Pergamon Altar and the Ishtar Gate of Babylon. The museums are best visited in the winter when there are fewer visitors.