Yes, there really was a castle on this hill!
The castle was built in 1868 by Capt. Henry W. Moulton of Newburyport. The castle included 22 rooms and a tower with battlements. The castle was of Gothic architecture and was built of wood to look like stone. Moulton castle was "long a landmark...the view is unsurpased" and 14 towns could be seen from atop the castle tower.
Unfortunately, the castle was torn down in 1900 but that is another story. The hill is now part of Maudslay State Park and parking is free if you use my parking waypoints. A similiar castle built of stone still stands just 7.7 miles west--that is Winnikenni castle in Haverhill (see Castle Cache GC8438 if interested).
"You know, Moulton, you never could build a house on that hill; you could not get a road up there; too steep." So said the locals in 1868. Capt. Henry W. Moulton, returning from the Civil War, did not listen. He did indeed build his castle. Moulton was a local boy. His relatives still farm Arrowhead farm at the foot of the hill; the farm has been in the family since 1683. Moulton himself founded the United States Carriage Factory in Newburyport and helped start an early trade and industrial training school or "Mechanics Library Association". He also apparently served as a representative to the General Court from the 1st district. Captain Moulton was appointed a U.S. Marshall to Idaho by President US Grant and while he was gone the British Minister Sir Edward Thornton spent 4 summers at the castle. Other famous visitors included local poet John Greenleaf Whittier and the public were alway welcome to tour the grounds in Moulton's day.
In 1883 Capt. Moulton held a reunion at the castle for the surviving Civil War veterans of his 32nd Mass. regiment. There was a steamboat river tour and a banquet was held on a tent in the lawn. A 16 gun salute was fired from a cannon on the hillside.
In 1896 the castle was purchased by the Mosley family as part of their expanding estate. They tore it down soon thereafter claiming to reporters that it "was picturesque from a distance but was unfit for habitation without very extensive repairs" (1901 newpaper). This may or may not have been true: the Mosleys had a penchant for tearing down existing buildings in the future park both to return the land to its natural state and to avoid paying taxes on the improvements.
Like much of NE parkland, the castle site at the top of the hill is heavily overgrown with poison ivy in summer, but I have specifically selected a wooded site on the side of the hill which is poison ivy free year round, this includes access on the 2 track trail winding up the SE side of the hill. The short 30 foot bushwack off the trail is extremely steep up the hill to GZ but also poison ivy free. After finding the cache, I encourage all to continue to follow the trail to the hilltop and along the ridge for some fine river overlook views. If you are under 5 feet tall seeing the castle cache may be tough due to the line of sight angle required. I have added a log to stand on to help.