It is around 13,5 km from Prague Ruzyne Airport to City Center.If you take taxi(quite expensive) or public trasport ( i prefer http://dopravce-pragueriders.webnode.cz/) it is around 45 min aprox.,...
a little over 30 mins It takes 25 from airport to closest metro station (sadly, the shortest metro branch is the one leading to airport). And it is 5 mint to Staromestske namesti (old city town...