Answer:

Grey Towers.

Grey Towers, a mansion that is now part of Arcadia University, was built in 1893-1894 for William Welsh Harrison, co-owner of the Franklin Sugar Refinery in Philadelphia.  Harrison decided to build the mansion after his previous house, Rosedale Hall, was destroyed by fire in January 1983. Harrison hired 23-year-old Philadelphia architect Horace Trumbauer to design a grand new house on the same 138-acre site in Glenside, PA. 

Trumbauer took inspiration from Alnwick Castle in England, the medieval seat of the Dukes of Northumberland, and from the grey stone found in Chestnut Hill, Philadelphia.  The estimated construction cost of the new residence was $250,000, which included the most modern conveniences of the time, especially electricity.  Grey Towers is most recognized however, for its eclectic design, copying French styles from the Renaissance through the lavish age of Louis XV.  Embellishments to the mansion included walnut and mahogany paneling, enormous tapestries, marble mosaic fireplaces, massive glass sliding doors, and domed, painted ceilings.  When completed, Harrison owned one of the largest homes in the country, and one of the greatest castles in America, with more than 40 rooms.

Harrison died in 1927 and in 1929 Beaver College (now Arcadia University) purchased Grey Towers for $712,500.  To appropriately recognize its historic and architectural importance, Grey Towers was declared a National Historic Landmark in 1985.