A Michelangelo work that has not been shown in public for 50 years has gone on permanent display at the new Harley Gallery in Nottinghamshire.
The Madonna del Silenzio (Madonna of Silence), created in 1538, is part of the Cavendish-Bentinck family's Portland Collection.
The gallery, on the family's Welbeck Estate near Sherwood Forest, also has works by Van Dyck and George Stubbs.
A pearl earring worn by Charles I at his execution has also gone on show.
The current head of the family and grandson of the 7th Duke of Portland, William Parente, said the collection had been "painstakingly assembled over the last 400 years or so".
"These things are our history; each generation learns from them and adds to them if they can.
"But they are also part of our collective history as people; they chart the way people, places, tastes and society have changed - everyone should be able to enjoy them."
Alongside the painted masterpieces, the 800 sq m gallery also houses miniatures by Nicholas Hilliard and Christian Friedrich Zincke, Meissen porcelain and jewellery by Cartier. ?BBC