YYou can travel anywhere in Europe by air. Major cities such as Paris are often served by more than one airport, and so you can choose the one that is most convenient for your needs.
Once you have landed at the airport of your choice, you will find that many cities have metros (Vienna, Berlin, and Paris are just a few examples) whilst other cities (such as Bratislava) have great bus based public transport systems.
It is worthwhile investigating and planning your onward travel options before you arrive, as then you can find the cheapest deals – there are lots of great travel options in European cities for tourists.
For example, if you are visiting Vienna for two days, you can get a ticket that enables you to enjoy unlimited travel for 48 hours on the city’s network of trams and underground trains.