Underground cool: Spreetunnel Friedrichshagen

The tunnel under the Spree has been around for almost 100 years. At 120 metres long, it connects the Kämmereiheide near Köpenick with the Müggelpark in the district of Friedrichshagen. It was built because a bridge would have been too disruptive to the (then) booming shipping industry. So instead of a beautiful view of the Spree, we have this cool, damp tunnel. Awesome. Other tunnels in Berlin can also provide respite from the heat, and some have even more fascinating histories – more on that later.
Hang out in Berlin’s deepest Bahnhof

Did you even go to Berlin if you didn’t get a selfie in front of Brandenburger Tor? Visitors to the Hauptstadt are naturally drawn to Pariser Platz and Tiergarten (Berlin’s most underrated park). But did you know that 17 metres below the crowds is Berlin’s deepest U-Bahn station? At such a great depth, it is said to be an average of 10 degrees colder than on the road above.
Neues Museum

Excursions to the museum are not just for rainy days. In the well air-conditioned and partly windowless rooms of the Neues Museum you can escape the inferno outside. Part of the effect may be psychosomatic though; numerous exhibits showcase metal and stone artifacts from prehistory and early history as well as antiquity. Most of the great museums in Berlin are reasonably air-conditioned(!) – temperature extremes are terrible for the longevity of art.
- Neues Museum Bodestr. 1–3, Mitte, more info here
The taxidermy room at the Naturkundemuseum

Thirst for knowledge and cooling off under one roof: in the taxidermy room of the Natural History Museum, various taxidermy techniques are presented and various animal plastinates from the workshop of the notorious Gunter von Hagens are on display. Due to the nature of the exhibits, the hall is well air-conditioned and perfect for taking a breather before heading back out into the heat.
Cryotherapy, because why not?

The cold is good for you. Ask any startup crypto-bro and they will tell you the benefits of journaling and cold showers. But why not take it a step further? During cryotherapy, you stand in a cold sauna for two to three minutes, in which time the temperature is reduced to minus 110 degrees Celsius. It doesn’t get any colder. The Berlin companies ‘CTB Fit’ and ‘Formwandler’ offer cold chambers, if you’re keen. Apparently the purpose is not to cool down well, but to burn calories, but that’s probably a good idea too.
Chill in the Keller

Every apartment in Berlin has a basement. The temperatures down there are bearable, especially in old buildings. Not so sure about the atmosphere though. Maybe you can use the opportunity to tidy up and dispose of that junk you accumulated between WGs? You might even find something worth selling at a local Flohmarkt or on eBay Kleinanzeigen.
Get a quote from your local Klimaanlagenhersteller

When Berliners start suffering from the heat, air conditioner dealers reap the benefits. You don’t have to buy the most expensive device right away – a demonstration could be enough for the time being. Think of it as a test drive.
Cool by nature: Berliner Unterwelten

This is where cool temperatures and Berlin history come together: the Berliner Unterwelten regularly offer guided tours through tunnels and bunkers. The bunker at Humboldthain or the AEG test tunnel – the first underground railway tunnel in Germany – is our pick of the bunch.
Bonus tip!
Still too warm? Reddit user /u/jessepinho created this map of all of the places with Klimaanlage in Berlin. There are nearly 400 locations, and the list keeps growing! Thank you /u/jessepinho!
Still too hot? Make a beeline for one of Berlin’s open-air pools or the city’s loveliest lakes.