Plans for a business park in Durham, creating at least 4,000 jobs, have been submitted.
Durham County Council wants to build the park on the current site of County Hall and neighbouring land.
Councillors have previously agreed to move to new headquarters in the city centre and that development will house 1,000 staff.
Should planning permission be granted, work on the business park would begin in 2021.
Simon Henig, leader of the Labour-controlled council, said: "We are looking to provide a modern central business location, in a mature parkland setting, within walking distance of the mainline train station and city centre."
Plot C is proposed to provide up to 38,468sqm of floorspace divided into six plots consisting of office buildings and car parks.