We visited Viareggio during Carnivale and stayed at the Grand Hotel Royal. It is part of the Best Western Brand and is considered a 4 star from their standards. Do not think of those 1 and 2 story rather sad motels in North America. The Best Western in Europe is a brand encompassing many independent more boutique style hotels.
It is located on the shoreline, along the promenade, in a very pretty historical building complete with turrets. There was a recent refurbishment and the hotel re-opened in March of 2014. There is a beach and an outdoor pool which could be lovely depending on the season you are visiting in. The hotel staff was friendly and the breakfast menu had a nice variety, which is not usual for most Italian hotels given that breakfast usually is made of a freshly squeezed orange juice (spremuta), cappuccino and a brioche (equivalent of a croissant).