There is a huge rat community in Stockholm. They are almost everywhere. I have met them at the inner city in Södermalm, in the suburbs of Solna and even in the posh Östermalm. The common thing is that you need to run or drive with your bike faster than the rat does. Otherwise there is an unwanted meeting with this sometimes even cat-sized creature.
I just read from the local Solna News that there are kids playing with the dead rats in one playground of the Solna city. Come on! Things cannot continue like this. I have even heard that these smart creatures can climb up in the plump systems. Who knows when you are going to meet them in your pretty bathroom when you next time need to go.
Some people say that there are rats because of the too wide and wild grean areas in Stockholm. I don't think it is the reason behind. The reason behind is that there are too much to eat for these creatures. People leave their carbage irresponsibly in the streets and that is the most thing that attracts the rats. In addition there haven't been enough campaings to get rid of them either.
We used to have a problem with city-bunnies in Helsinki. Bunnies, thought they were quite cute, were everywhere in the parks and streets until we decided to get rid of them. In the end everyone was happy and especially the lions in the Korkeasaari-zoo where the dead bunnies were transported.