2 free days...where are the coolest places to visit?

If you like stark angles and shapes, then both the Holocaust Memorial and the Jewish Museum Berlin will give you a place to play. Plus, they're both historically significant.

Museum Island is another place to pass the time on a rainy day, but also to capture stunning photos. It's near the St. Hedwig's Cathedral which is also beautiful to photograph.

If you love nature, stroll through the Tiergarten and check out the Zoologischer Garten.

For history, check out Checkpoint Charlie and the Berlin Wall - the memorial has a fantastic wall of history along it that is really interesting.

It's off the tourist route, but I loved the artsy area on Kastanienallee just south of Eberswalder north of the city center. It's full of quirky art and cafes. I just wandered around aimlessly until I ended up in the city center, but in Berlin, you can do that and you'll find some really cool things.

Rent a bike and ride all over the beautiful, flat and eminently bikeable city stopping at the KaDeWe for lunch, the huge flea market next the Zoologischer Garten, through the Tiergarten to the Brandenburg Gate. Wander around the hip Prenzlauer Berg and Friedrichshain neighborhood and admire the old apartment building drinking a milch kaffe. Then your second day you might consider trekking out to Sachsenhausen the concentration camp just outside the city.