The tradition has spread all over Germany, but you won't get the genuine thing anywhere else but in Munich: Biergärten.
In earlier times when brewers were desperate to keep their beer cool during the summer, they stored their barrels in cellars and planted chestnut trees above them, since their wide branches and large leaves keep the place nice and shady. King Max I. Joseph granted the brewers the right to sell their beer on the spot - but not food. Since then, the people of Munich have flocked to these gardens to drink fresh beer straight from the barrel, bringing along their own food.
As soon as the sun comes out in spring and temperatures rise above 15°C (60°F), the inhabitants of Munich flock to the large chestnut gardens, usually seating a few thousand people, and socialise over a litre of beer. Yes, a litre - the one-litre (2 pt) mug is the minimum amount available, and with about 5% of alcohol Bavarian beer is as strong as any European beer, so you had better get home by public transport or walking. However, there is also shandy called "Radler" (lager beer mixed with lemonade) and several sodas available for drivers. Still, you shouldn't be surprised at seeing locals consume several of these litres on a single evening: beer is regarded as a basic part of nutrition in Bavaria, not actually alcohol.
Nowadays beer gardens also sell food, and are usually affiliated to a restaurant. However, the B-Y-O tradition is kept alive, and thus beer gardens have both tables with tablecloths, where you are served by a waitress, have to buy restaurant food and are expected to leave a tip, and innumerable long tables and benches without tablecloth, where you consume what you've brought. You can also buy traditional Bavarian food such as "Obatzda" cheese, grilled ribs, potato salad, Brez'n and other specialities from self-service shacks. But real beer garden professionals never come without a basket stuffed with bread, cucumbers, horseradish which is cut in an elaborate spiral, homemade Obatzda, grapes, ham, sausages and whatever else takes their fancy. Plates and cutlery from home, sometimes even a tablecloth bearing the Bavarian white-and-blue diamonds and candles for after dark nibbling ensure Bavarian "Gemütlichkeit": this concept, central to the Bavarian mentality, translates best as "cosy and relaxed sociability". Just sit down at one of the tables with locals - it is a custom in Bavaria, whether in beer gardens or restaurants, to sit down with complete strangers and enjoy each other's company - they might even end up sharing their food with you. And if you go to a beer garden, don't expect to spend less than two hours there - this sanctuary to the Bavarian way of life has preserved relaxation in defiance of hectic modern life.
There are about 180 beer gardens in Munich, but be careful: a lot of restaurants put up a sign "Biergarten", only meaning that you can sit outside in a garden off the street, but staff are not amused if you bring your own food.
Some of the most popular genuine beer gardens are:
Tel.: +49 (0)89 59 43 93
daily 11.30am - 11.30pm
Public Transport: S-Bahn stations Hauptbahnhof or Hackerbrücke
Sondermeierstraße 1 (northern part of Englischer Garten)
Tel.: +49 (0)89 32 52 24
Tuesday - Sunday 9am - 11pm
Public Transport: U6, exit Studentenstadt or Freimann, then walk for 10 minutes
Chinesischer Turm (Chinese Tower)
Tel: +49 (0)89 38 38 73 27
daily 10am - 10pm
Public Transport: U3, U6 Giselastraße, then Bus 54 or 154 to "Chinesischer Turm"
Hirschgarten 1 (near Nymphenburg palace)
Tel. +49 (0)89 17 25 91
daily 9am - 12am
Augustiner, Schloßbrauerei Kaltenberg and Hofbräu Tegernsee
Public Transport: S-Bahn, exit Laim, walk via Wotanstraße or Tram 12 or 17, exit Romanplatz or Steubenplatz
Tel: +49 (0)89 15 68 27
daily open until 11pm
Spaten Bier and Franziskaner Bier
Public Transport: U1 exit Gern