These include Vienna (capital of Austria), Bratislava (capital of Slovakia), Budapest (capital of Hungary), Belgrade (capital of Serbia), and numerous other large municipalities. Historically, the Danube was an exceptionally important river to the Greeks and Romans.
At that age, kittens are eating on their own and going to the bathroom on their own, so they can be away from mom for a day while she gets fixed. If mom is feral, when the kittens are 5 weeks old, that is the point when you can get mom spayed and release her right where you trapped her. Kittens can be safely fixed as soon a they hit 2-3 lbs., which is generally between 8-12 weeks.
In the case of feral cats, the kittens may have been taken from the mother for taming. Kittens should not be taken from the mother before 5 to 6 weeks of age if possible. (For wild kittens you may want to take them away from the mother at 4 weeks to tame them.