By 1912, they had fashioned a series of ornate terraced gardens, and had begun work[4] on a magnificent grass mall, 160 feet (49 m) wide and lined with evergreens cascading from the top of the hill straight down to the water nearly half a mile away.

Classical-style statuary flank at regular intervals this "Grande Allée", the design of which was taken over in 1913 and finished in 1915 by Arthur Asahel Shurcliff[5][1] after Crane dismissed the Olmsted Brothers.

[4] An opulent "casino" (Italian for "Little House") was built at its midpoint, replete with saltwater swimming pool, bathhouse, guest cabanas and a sizable indoor ballroom.

The villa’s stucco construction simply couldn’t handle the harsh wind, rain, and snow of New England, especially due to its exposed location on the top of the hill.

"Upon the summit Mr. Crane has erected his splendid summer home, with a beautiful sunken garden, rose garden, lawns and terraces, commanding a marvelous view of land and sea, of Agamenticus and Boar's Head and the low-lying Isles of Shoals on the distant horizon, Bar Island and the long bar with its many lines of white breakers, sand dunes and the level beach near at hand.

Designed by architect David Adler of Chicago, the new fifty-nine-room mansion included a main facade in the 17th-century Stuart style, a library with Grinling Gibbons carvings imported from an English country manor (Cassiobury House), parquet wood flooring, and paneled interior rooms from an 18th-century townhouse at 75 Dean Street in London.

A pair of immense seated griffin statues by renowned sculptor Paul Manship grace the entrance to the north terrace overlooking the sea.

The property was used as a forum for outdoor concerts in the late 1950s and early 1960s, featuring such jazz legends as Louis Armstrong, Ella Fitzgerald, and Dave Brubeck, and as part of a Castle Hill Art Center and music camp run by the New England Conservatory.

The Trustees continue to offer a number of public programs throughout the year, including outdoor picnic concerts on the Allée, and Christmas events.

[9] The 1987 movie The Witches of Eastwick prominently features the grounds and mansion at Castle Hill, the site filmed on location as home of the eccentric millionaire Daryl Van Horne, played by Jack Nicholson.

The 1994 movie The Next Karate Kid also features Castle Hill as the Buddhist monastery Mr. Miyagi (Pat Morita) takes Julie Pierce (Hilary Swank) to after she is suspended from school for 2 weeks.