The feature has been named after Orpheus from the Greek myths
A large garden feature has been sculptured out of the parkland surrounding Boughton House, Kettering.
The 50m by 7m inverted pyramid has been named after Orpheus who travelled to the underworld in the Greek myths.
Designed by Kim Wilkie, it is the first new garden feature at Boughton House for around 300 years.
Orpheus is meant to echo the Great Mount which towers alongside it. That is a grass-covered pyramid which dates from the 18th Century.
Earth-moving equipment was used to construct the 'inverted pyramid'
Orpheus is also covered in grass. A ledge spirals downwards to a square pool at its base.
Wilkie's inverted pyramid was inspired by the neighbouring Great Mount and its connection with the Greek myths.
Wilkie said: "The proposal was to make a space that emphasises the scale and mass of the great earthwork, to create an Orphean Hades to complement the Olympian Mount."
In the myths, Orpheus was born close to Mount Olympus and journeyed to the underworld. The 21st Century version has a square pool at the bottom rather than Hades.
Boughton House is home to the Duke of Buccleuch and Queensbury. In 2028 the Duke's family will have lived at Boughton for 500 years.
The park is Grade I listed
It was once a monastery
There have been 10 Dukes of Buccleuch
Charles Lister, from Boughton House, said the new feature complements the restoration of the gardens, which date from the 1720s.
"The Duke wanted something that was modern but still in keeping with the rest of the landscape. It is a 21st Century feature in the middle of an 18th Century landscape."
Alongside Orpheus is a polished steel cube frame and a shallow rectangular pond. Spiralling out is a water-filled channel, or rill, which is based on the Fibonacci sequence.
This is an infinite series of numbers (0, 1, 1, 2, 3, 5, 8 etc) in which each number is the sum of the previous two.
The creation of Orpheus and the restoration of the gardens are being paid for by the Duke. The cost has not been revealed.
The gardens at Boughton are open to the public from 1 May to 1 September. The house is open during August.