What are some fun and interesting things to do in Berlin?

We are a couple in our 50s who hope to spend about 5 full days in Berlin. What are some fun things to do in Berlin? We will not have a car, so need to rely on public transportation. What is the best way to get from the airport to downtown Berlin? Any hotel recommendations? How would you suggest to plan our days? We... show more We are a couple in our 50s who hope to spend about 5 full days in Berlin. What are some fun things to do in Berlin? We will not have a car, so need to rely on public transportation. What is the best way to get from the airport to downtown Berlin? Any hotel recommendations? How would you suggest to plan our days? We like concerts, museums, parks, shopping. Thanks!
Update: Also, could you vote on this Tie-Breaker. It's an oldie, but goodie:
http://answers.yahoo.com/question/index;...
Update 2: Why did Mrs. Cullen get so many thumbs down for the answer? It seemed like a good suggestion to me. I notice a lot of answers in the Berlin section get handsdown thumbs. Am I missing something?
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