This looks like something from Brideshead Revisited. It's the Crane Estate, in Ipswich, Mass., built by plumbing-fixture mogul Richard T. Crane in the 1920s. The 59-room structure is sometimes open for tours. See: www.thetrustees.org.
It's close to the exquisite Crane Beach -- four miles of fine-grain sand backed by pitch pine forest on Ipswich Bay that's protected by a wildlife preserve. It's also close to the beautiful but often storm-battered Plum Island, named for the beach plums that flourish there. (See picture below.) But who knows if Plum Island will be there in a century, given rising seas and seemingly more frequent Nor'easters?