Rockliffe Hall is set on an 18th-century hunting and shooting estate on the banks of the River Tees on the border with North Yorkshire.
The estate's 19th-century Victorian Gothic hall has been turned into a 61-room hotel with event space.
It will offer eight meeting rooms and a banqueting suite with a private entrance and capacity for 250 guests.
The property claims to be the only hotel in England to have a ‘sleep retreat' and chromatherapy bedrooms with lights that move through a spectrum of colours to aid relaxation.
Rockliffe Hall has a 4,645sqm spa that will offer 12 treatment rooms, a VIP treatment suite, sound-wave relaxation room, hydrotherapy pool, eight thermal suites, and a 20-metre indoor pool illuminated by stained glass windows.
There is also an 18-hole championship golf-course, claimed to be Europe's longest.