A trolley tour with Viking should be the first stop on your Newport visit. Our guide was knowledgeable, informative and entertaining - and the time flew by. We took the Scenic Overview Tour (Tour 1), as we had spent the previous day touring the mansions.
In retrospect, Tour 2 - the Grand Mansion Tour - would have been a smarter and more cost effective approach. This provides the scenic tour, and admission to either The Breakers, Marble House or Rosecliff. Tour 3 includes two mansion tours.
Whatever tour you chose, you won't regret it!