For a city with such a turbulent history, Berlin is one of the most chilled out cities I've visited.
Talking of the trains, they are so easy to use - a travel card costs around 6.50 euros and the trains are frequent, clean and you don't have to battle to get a seat!
Of all of the things to see and do in Berlin, these are my top 5:
Walking Tour - we turned up for the free walking tour on a recommendation from a friend. Our guide on the 3.5 hour tour was Zabi, who was very knowledgable and enthusiastic about the city and its history. Starting at the Brandenburg Gate, Zabi led us to the holocaust memorial, the former site of Hitler's bunker, the Berlin Wall, Checkpoint Charlie, Gendarmenmarkt and Museum Island - to name a few.
DDR Museum - On a recommendation from the same friend, we visited this interactive museum and really envisaged what life would have been like living in the socialist state. And for any car lovers, you can even start an old Trabi.
Henne - Fried chicken, sauerkraut, potato salad, beer - all good. It's also right where the wall used to stand so have a look at some of the pictures in and around this pub too, really amazing.
Cafe Einstein - We ate breakfast here both mornings, Peter had been here before so knew what to expect. If you order the breakfast for two and get a selection of pate, ham, turkey, cheese, soft cheese, brie and a selection of breads. A good pot of green tea too!
KaDeWe - I couldn't go a whole weekend without visiting he second largest department store in Europe (Harrods is the largest). The window displays were beautiful and the building itself is well laid out and spacious.
I'd definitely go back to Berlin but possibly in the Spring/Summer so I can see the Tiergarten in its glory.