Bristol University's Goldney Hall, built in 1714, is set in ten acres of formal and wild gardens and is English Heritage listed.
The gardens were laid out by Thomas Goldney III and in recent years much work has been done to restore them in the spirit of his original design. The shell-lined grotto, a Grade 1 listed building, is widely valued for its unusual atmosphere and construction and will be open on the day.
The garden has other follies, such as a bastion, an ornamental canal, a gothic tower and a rotunda.
The open day will run from 2 to 6 pm. Tickets will be available on the door and will be priced at adults £2.50, concessions £1.50 and children under five free. Proceeds from the open day will go to the Goldney Restoration Fund.
Cream teas will be served in the recently refurbished Orangery, which overlooks the ornamental canal and formal gardens.
The Hall is frequently used as a film location, and has appeared in the acclaimed British film Truly, Madly, Deeply, as well as the BBC's Chronicles of Narnia,
Goldney Hall is located on Lower Clifton Hill, Clifton, Bristol.