The best way to help Berlin in the wake of the December terror attack? Keep visiting and show your solidarity with this very cool German city. And while you're there, you can find plenty of activities that don't cost a cent, writes Shandelle Battersby.
1 Play table tennis
It may surprise you to learn there are hundreds of tischtennis tables scattered around Berlin in public spaces, all free to use - although, of course, you need your own paddles and balls. If by some miracle you don't stumble across one, have a look at pingpongmap.net, get yourself some gear and a few bottles of bier, and go and play nicely with some Deutsch people.
2 Checkpoint Charlie
The former border crossing between communist East and American-controlled West Berlin during the Cold War era has been maintained as a tourist attraction. You'll see a replica of the former border house, "soldiers" in uniform, and recreations of the iconic signage in German, English, Russian and French warning people they were leaving/entering the American sector.
Checkpoint C (Charlie) was the crossing diplomatic personnel, US military and non-Germans used to get into East Berlin.
• Friedrichstrasse 43-45
3 Topography of Terror and Berlin Wall
This outdoor/indoor history museum is on the site of the former Gestapo and SS headquarters, which was destroyed by Allied bombs in early 1945. Adjacent is the longest surviving stretch of the outer Berlin Wall, which marked the boundary between the US and Soviet sectors. Inside is a permanent exhibition looking at the SS and police of the Third Reich; outside in the excavated trench of what was the former cellar of the Gestapo HQ, where many political prisoners were tortured and killed, is an exhibition looking at the impact of the National Socialist policy on the city and its residents. There are also free daily guided tours. topographie.de
• Niederkirchnerstrasse 8
4 Learn German
When in Rome . . . or Berlin . . . why not learn a little of the local lingo? The Goethe Institut offers free online classes as part of its "Deustch fur Dich" programme. These give you the opportunity to engage in interactive learning games to improve your German at all levels, learn interesting facts about the language from experts, take part in a helpful forum and find learning partners.
This former concentration camp, which translates to "House of the Saxons", was one of the largest used by the Nazis, followed by the Russian KGB after World War II. To get to Sachsenhausen from Berlin you need to catch the S-Bahn train to Oranienburg, which will take about an hour, then either walk for about 2km or catch a bus to reach the camp. Here you'll find a memorial museum and several surviving or reconstructed buildings and structures, such as guard towers, barracks and crematory ovens. Audio guides are available for a small fee.
6 Memorial to the Murdered Jews of Europe
A block from the Brandenburg Gate you'll find the striking and powerful Holocaust Memorial designed by American architect Peter Eisenman and engineer Buro Happold, also known as the Memorial to the Murdered Jews of Europe. Set on a sloping 1.9ha field, the memorial is made up of 2711 huge concrete slabs in varying heights assembled in a grid pattern. Eisenman said he "wanted to create an illusion of instability in an apparent system of order", and show "how this system is futile in time". Leave yourself time for a free guided tour of the excellent underground information centre.
• Cora-Berliner-Strasse 1, stiftung-denkmal.de/en
7 Reichstag Dome
You have to be organised to get on the roof of the Reichstag building to see its famous Norman Foster-designed dome by registering in advance for a set time, but it's worth a little (easy) online admin for the amazing 360-degree views up top of the government district. A clever motion-sensored audioguide will supply you with interesting facts about the building and what you're looking at as you make your way up and down the glass dome set atop the building that houses the German Bundestag (national parliament). It's open until midnight every day, so if you go at dusk you'll see the twinkly transformation of the cityscape into night. If you don't have access to the web, you can also register at a small building close to the building's southern entry.
• Platz der Republik 1, bundestag.de/en
8 Alternative Berlin tour
Berlin is definitely edgy, a little bit raw, a little punk. If you don't have friends there, one way to get a good look at the underground culture is via a free tour with Alternative Berlin, who promise to take you off the beaten track. This involves a free walking tour twice a day that takes in skate parks, street art and urban art projects, artist squats, cultural icons and music landmarks. You don't need to book but tips are welcome. Meet at 11am or 1pm daily at the Alexanderplatz TV Tower, next to the tower entrance in front of Starbucks.
9 Berliner Philharmonika
This venerable organisation is doing a great thing for the people of Berlin by playing free concerts on Tuesday lunchtimes in its foyer. The Lunchkonzerte (Lunchtime Concerts) run for 40-50 minutes and are aimed not only at residents who want something to do in their breaks, but at weary tourists who need some time out. Numbers are limited to 1500 and there is some food available for purchase. Donations to Unicef, the philharmonik's affiliated charity are gratefully received.
10 Strandbad Wannsee
Known as Europe's largest lido (public beach), the Strandbad Wannsee lies on the eastern shore of Berlin's Havel River, about 40 minutes from the city and is said to be Europe's "largest outdoor swimming area on an inland body of water. The sand is not completely natural - part of the beach is widened using the golden stuff from elsewhere, but the area is listed as a Cultural Heritage site. On site is a nudist section (Strandkorbs), and a playground, park and promenade.