Hemel Hempstead police station’s year-long £2.5million refurbishment is due to be completed in October.
The 60-year-old building, in Coombe Street, has had a new roof, façade, windows, and a heating and electrical systems installed.
New internal offices, public spaces and interview rooms have also been created or given extensive renovation.
Police and crime commissioner David Lloyd said the work had secured the future of the station.
He said: “This will greatly improve the working conditions and facilities for officers, staff and members of the public.
“Residents in Hemel Hempstead wanted to keep an operational police station in the centre of the town and this investment has guaranteed that.
“I look forward to coming back in a few months’ time for the official opening at the end of October.”
While the year-long project has been under way, the station has remained fully operational from temporary cabins over two floors on the site.
Members of the public have still been able to attend appointments while the work has taken place.