Country/states/city script

We need EXISTING script where all countries, states, cities worldwide are. If you have existing script or if you know a site who use it, THan foward us that URL pls so Eg. if you click on country pull down you see ALL countries in world. If you select eg. 'GERMANY' than appear all german states, if you select 1 'german state' than appear ALL major cities from that state Do you have EXISTING script or know WHere can we find this script? Thanks