Buy the welcome card - you can purchase it in advance (and pay a hefty shipping fee) or buy it at the airport at Gate 13. It provides 50% off of attractions and free subway transportation for the time period that you select.
Don't hesitate to try the bus system or subway. Both are inexpensive, intuitive, quick, and user-friendly.
Full report at www.travelmusings.net
City bus tours can be expensive but routes 100 and 200 in Berlin are regular (double-decker) services which pass most of the main sights in the city centre. Buy a pack of tickets (which can also be used on the S-bahn and U-bahn) and get on and off where you want.
A day (or more) ticket (Tageskarte) is the most economical option and can be bought from most BVG ticket offices, such as the one at Zoologischer Garten (Zoo).
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