The United States Riviera Recreational Area provided American soldiers with the rare opportunity to enjoy "a millionaire's vacation for peanuts."
Following the invasion of Southern France in August 1944 the Allied armies raced northward in pursuit of Axis forces retreating towards Germany. By October 1944 the American Sixth Army Group, commanded by General Jacob Devers, began converting Nice into the premier rest area for G.I.s. The resulting United States Riviera Recreational Area (U.S.R.R.A.) took full advantage of the renowned hotels, entertainment, and sea front, but also relaxed traditional rules of Army discipline in order to make each soldier's visit to the U.S.R.R.A. as enjoyable as possible.
At the U.S.R.R.A. soldiers were billeted for a nominal fee of 100 francs (i.e. $2) in some of the finest hotels in the world and could visit bars and nightclubs or take excursions to nearby towns. Rules were minimal, curfew was at 1:00 a.m. and saluting was banned. By June 1945 over 6,000 American soldiers a week were enjoying everything the U.S.R.R.A. had to offer and a general sentiment was that it was "the best thing the U.S. Army ever did."
One soldier who visited the U.S.R.R.A. around this time was Private First Class George L. Johnson, who served Cannon Company, 399th Infantry Regiment, 100th Infantry Division. A letter Johnson wrote during his visit gives some perspective on how soldiers enjoyed their time at the U.S.R.R.A.:
Nice, France - 2 May 1945
Time - 2040
I am now a guest of the U.S.R.R.A. (United States Riviera Recreation Area) for 7 days. It's a kind of furlough. I am living at the Queen's Hotel and I have a private bath. The first thing I did when I got here was take a nice hot bath. The trip is [one] of several that the Army has to let us get some rest and fun. I like this Riviera deal the best though. There are lots of things to do here. Take today for instance. I went on a tour by bus and I visited Grasse. There is a perfume factory there so with you people at home in mind I purchased perfume. I got Ella some liquid perfume and I got you solid perfume. I hope you like it, because I don't know much about such things, I only buy it.
I am writing this letter from the Red Cross Club here in Nice. It is the most beautiful A.R.C. club in the E.T.O.U.S.A. In fact I bet it's the finest in the world. Before the war it was the finest gambling casino in Nice and it is really something to see. There is a complete theater within the building, several ballrooms, a snack bar, a huge lounge, and many other rooms for the A.P.O., barber shop, package wrapping room, Coke bar and other things. I had my first "Coke" in about 7 months here yesterday. It was pretty good too.
A few nights ago 3 of us went out and got tight on champagne. It cost us 400 francs a bottle and it took 6 bottles to do the job but it was worth it. The trouble with wines is when you get up in the morning and take a drink of water you are lit all over again. The champagne is not the best I have tasted though, in Germany there is better stuff. The Germans also have beaucoup schnapps, vermouth, and other wines. I was drinking some 1929 Tokay just before I went to Heilbronn.
Nothing more to write so I will sign off.
P.S. Hitler is dead. Hot dog. 
The Army provided a variety of guides to soldiers visiting the U.S.R.R.A. Several are available for free as pdfs. (click the bolded wording to view each document).
Don't SNAFU Your Leave! (courtesy of the North Carolina Digital Heritage Center).
Welcome to the Riviera (courtesy of the 284th Engineer Combat Battalion).
The Thérèse Bonney collection at the Online Archive of California has a series of photographs taken at the U.S.R.R.A.
 “U.S. at War: G.I. Heaven.” Time. Time Inc., June 18, 1945. http://content.time.com/time/subscriber/article/0,33009,775896,00.html.
 George L. Johnson, letter dated May 2, 1945. Author’s collection, 1-4.