The ubiquitous double-decker red buses you see in most big cities exist in Copenhagen as well. In addition to the city tours, you also get access to a boat ride as well.
Don't be fooled by the "24 hop on hop off bus and boat tour" verbiage, as the huge asterisk here is you only get ONE boat ride. So, if you jump off somewhere that looks interesting, you can't ride another boat- unless you pay.
The previous complaints I read before writing this review all pointed to lack of communication and bus availability, which I had no problems with. I do think the price of $40 USD for 24 hours is pretty steep, taking into consideration this is Copenhagen, and almost everything is expensive- it seemed pretty normal.
The hop on hop off bus tour is the same as it is everywhere else. You basically pick a line (Copenhagen has the red, blue and green lines), depending what looks interesting to you. The most popular (and one we took) line is the red one, the "Mermaid tour", which naturally stops at the Little Mermaid statue (underwhelming, yet required if visiting).
There is free Wi-Fi on the bus, as well as free headphones, in which you can listen to commentary (in ten different languages) of the history and sites as you pass them.
We didn't have any problems finding or waiting for a bus, and the river boat ride was most definitely the highlight. It was really cool to see the city from that perspective, and how all the locals were enjoying the supposedly super rare sunshine-y weather they had that day (in June).
I don't have any complaints about the bus, and I would take it again. Sure, it's touristy AF, but I was a tourist! Nowhere else could I get a quick tour of the city, with a pre-recorded explanation of it. read more