Stourhead House

the inspiration for Lady Penelope's mansion

a view of Stourhead House main entrance a view of Lady Penelope's mansion
Stourhead House, Stourton, Wiltshire, main entrance, inset still from Trapped in the Sky
[ photo Josep Renalias — own work, CC BY-SA 3.0]
Not many people may be aware of the fact that the outside of Lady Penelope's mansion was based on an existing stately home with the name of Stourhead House and located in the county of Wiltshire in the south of England. A quick trip to the inimitable Wikipedia yields the following summary:
Stourhead is a 2,650-acre estate at the source of the River Stour in the southwest of the English county of Wiltshire, extending into Somerset. The estate is about 2½ miles northwest of the town of Mere and includes a Grade I listed 18th-century Neo-Palladian mansion, the village of Stourton, one of the most famous gardens in the English landscape garden style, farmland, and woodland. Stourhead has been part-owned by the National Trust since 1946.
The complete Wikipedia entry can be found here.