There are both voltage converters (230 volts E.U. to 120 volts U.S.) as well as plug adapters that allow an "U.S." plug to access E.U. wall outlets at the 230 volt currant. Check your electric needs for some have both voltage acceptability such as certain computers. Most higher end hotels we have stayed in Europe has one 120 volt wall outlet. The outlets are labeled as such. Rick Steves has a full line on his web site.