Getting wet: Swimming pools in the city
On a day like today, sunny, blue and pushing 32°C, you really don't want to be spending your time hanging out in cafes or trekking the tourist routes through the city. No, on a day like today you want to pulling on those Speedos and getting wet.
There are a large number of options for that in this city. Most obvious are the indoor pools. If you want to find one near you, try this webpage and click on Hallenbad. Generally though these aren't cheap: 4€ per visit, or 2.50€ if you are there before 8am or after 8pm.
Like most things, use of swimming pools has its own set of societal rules. Firstly, you are expected to shower before getting in the pool, which you do quickly in your swimsuit before running out. Secondly, if you are trying to swim laps it is every man for himself.
The pool is a war zone in Germany. It is a place where people define "this black line here is ALL MINE" and will swim up and down along it, ignoring the fact that they then charge into people coming the other direction. Lap lanes rarely exist because people rarely understand the concept of using it like a road and going up on one side and down on the other. Expect to cop an elderly woman's elbow to the ear as she forces her way past you, or to realise in panic that six people are bearing down on you, with no way to squeeze past.
However, there is no need to fear unless you're trying to do some training. As they say, Sport is Mord (sport is murder), but hanging out and getting wet... well that's just fun.