Blenheim Palace is a country house in Woodstock, Oxfordshire, England. It is the seat of the Dukes of Marlborough. Originally called Blenheim Castle, it has been known as Blenheim Palace since the 19th century.Its the only building called a palace which is not an actual palace.
 
Interesting facts...
The Marlborough title is one of the few in England that can pass through the female line. John Churchill’s daughter, Henrietta, became Duchess in her own right.
The Grand Bridge, designed by Sir John Vanbrugh, contains concealed rooms and passageways. When the lake was drained, original stairways, tunnels, fireplaces, and even 18th-century graffiti were discovered inside