Names and Places in Greek Languages

I start this thread because I have met many Greekish names of persons, places and events which are not so familiar to other languages.
When I find one very hard to understand which is which, I will post one by one.

2011.02.24
1) Ρουκαρία -- Roucaria, Rocaria: I can not find this name from Internet sources, please tell me, is it a French place, Italian place or Servian place?
2) Δούναβης -- Dounabe, Donabe : I know it is English Danube, but I want to ask why there are so many different vowells. Which version is more authentic?

2011.03.30
1) Λείριο, as a river, refers to Garigliano river in Italy, which is composed of two steams: Gari and Liri.