Have you ever done a free city tour before?
The advantages of a free city tour (besides not costing anything!) is that they are usually run by young enthusiastic people who know a lot about the city, the history and the culture. Besides giving the tour, they are more than happy to give you ideas for bars, clubs or places to go that are off the beaten path.
Although it’s free, the idea behind it is that you tip what you think the tour was worth. It beats prepaying for a tour and not knowing what to expect or feeling that you paid too much for what you got.
Make sure to turn up early, especially if it’s summer- the tours can get crowded!
My experiences and reviews:
Berlin – 8/10. It’s quite history heavy but that’s a given in Berlin. 3.5 hours covers a lot! Best to book a place in advance.
Ljubljana – 9/10. It’s a small city so you can cover most things with this tour. No need to book.
Budapest – 8/10. Be prepared to walk up a hill on the Buda side! Offering many types of other free tours such as a Jewish quarter walk or a Communist walk.
It's an EU thing 
It’s a great way to discover a city! I can also recommend the one in Prague, taking you through the Jewish quarter as well as through the old town center.
I like the photo of Bratislava that you put as the header photo. 🙂
Nice that you recognise it, it’s not one of the most known views in Europe 😉