If you're looking to learn about the history of the Gilded Age, there are various mansions that you can visit, including The Breakers, The Marble House, The Elms, Chateau Sur Mer, and Rough Point. (You'll be seeing Rosecliff without having to pay the admission fee!)
This is a beautiful 3.5 mile walk that hugs the Atlantic Ocean and will bring you right through the backyards of the Mansions.
Thames Street is the center of Newport's downtown/waterfront area. It is lined on each side with countless bars, restaurants, shops, and historic homes.