There are certainly more than sechs (6) reasons to love Berlin - in fact the list could almost be endless. But for efficiency's sake, here are just a few reasons to go. As the Germans say - Viel Spaß!
History hits you around every corner. The term 'historic' doesn't even begin to cover the stories you can encounter in this most past-laden of cities. There is enough here for even the most committed uber-geek to get his historic teeth into. Try visiting Charlottenburg Palace - a former royal residence - for a taste of the 17th and 18th centuries. Entry to the palace costs a small fee, but the extensive grounds are free. You could then take a trip to the Bundestag - German Parliament - and for a 15 minute wait, you are whisked to the top of the building, free to roam around on its roof. The last 150 years of German history are neatly encapsulated in a display inside the wonderfully remodelled glass dome. Views across the city are stunning - and you can even see parliament sitting below you if you are lucky. You can't do that at Westminster!
Grünewald Station offers a more sober and reflective experience of Berlin's past. It was from this station that thousands of Berlin jews were transported to concentration camps by the Nazis during World War Two. Take a train to the (still working) station and follow the signs to "Gleis 17". There, the unused tracks are engraved with the numbers deported and the final destinations they were taken to. It is a quiet, fitting and moving memorial.
The Tiergarten. Wander through its magnificent woodland right in the heart of the city. One of Europe's great urban parks, the Tiergarten was historically a game reserve, and now hosts Berlin Zoo next to its dense forest and formal gardens. This is Hampstead Heath and Regent's Park rolled into one - on steroids. There are over two square kilometres for footballers to meet for casual games, couples to stroll amongst the trees and drinkers to lounge in the Cafe am Neuen See next to the lake of the same name. After 15 minutes, you'll just about forget that you are in one of Europe's major capitals.
Walking and cycling is a must. Berlin is extremely flat, so get out on two feet or two wheels to truly appreciate what it has to offer. Many sights are within easy reach of each other - try a route from Potzdamer Platz to the Tiergarten, taking in the Brandenburg Gate, Berlin Wall and Reichstag en route. Bikes can be hired from Fat Tire Bike Rentals at the enormous TV Tower in the east and Zoo U-Bahn in the west. They'll even give you free helmets and locks. And if you're feeling weary, the U-Bahn and S-Bahn are quick and reliable alternatives.
Berlin is a cultural mecca. There are so many artistic influences and goings-on in Berlin it is mindboggling. With the Kulturforum home to the world famous Berliner Philharmoniker (with English conductor Simon Rattle), no less than three opera houses and the New National Gallery there is plenty for traditional culture vultures. Add in a mix that includes a burgeoning Jewish quarter (Europe's fastest growing) and a heady alternative scene amongst young Berliners and there really is something for everyone. For a quick peek into cultural Berlin wander down Unter den Linden past Madame Tussauds to reach the Deutsche Guggenheim - continue on and you reach Kunsthalle Berlin (Berlin's art gallery). Double back from there down Werderstrasse and you pass three magnificent cathedrals en route to the Konzerthaus Berlin. All within a square kilometre of each other.
This city takes beer very seriously. So seriously, in fact, that there's even a non-branded 'brand' of beer (called....well, "Bier"!) available as a counter-push against creeping commercialism. Other than that, you can enjoy all of Germany's more commercial beers at some of Europe's best watering holes. Try the aforementioned Cafe am Neuen See for a truly relaxed atmosphere - heated and cosy during the winter and with Berlin's biggest Biergarten for the warmer months. If you visit in early August, hit Karl-Marx-Allee as it plays host to the Berliner Bierfestival - although, be warned - there are over 200 breweries to sample from, so come prepared for a session!
Berlin is an interactive city. Whilst enjoying all the history and culture Berlin throws at you, you are encouraged to touch, walk, feel and interact with many of its sights. Walk through the famous Brandenburg Gate; follow the path of the Berlin Wall whilst touching the parts still left standing; take a quiet moment to sit on one of the black columns at the memorial for Europe's murdered Jews; indulge in some Ostalgie and climb into a traditional Trabi at the DDR museum on the banks of the Spree.
Whenever you go, and whatever you do - Berlin has got the lot. Have fun - Viel Spaß!