The Indoor Garden room at the Wilbur D. May Museum, in Rancho San Rafael park is the best formal party location in this city.
The room is beautifully appointed and needs very little decorating. There are live palms, ponds full of kio goldfish and a lovely waterfall. A banquet room in a casino could never come close to this!
I threw a hawaiian themed 25th wedding anniversary party for my parents there last year and every single guest was in awe of the beauty of the location. And at $450 for a 4 hour block of time, you cannot beat the price. They even provided tables to me, for free.
I highly recommend this location for any kind of formal or semi-formal event, such as a wedding reception or graduation party! But book early, this place is Reno's best kept secret!