Ruins of an old stone house, located on Scarborough Beach in Narragansett, RI
I could never find much information on the history of these ruins but they are said to be remains of an old carriage house.
The ruins are located off Scarborough State Beach park (map below). Pretty easy to find since they stand out well on the beach. Make sure to wear suitable shoes and watch for poison ivy since there is a lot of overgrowth in the area.