Other recent work has seen new lighting and cameras installed, resurfacing carried out on Station Road and murals added at Welbeck Street and Tickle Cock Bridge.
Planning permission for the Beancroft Subway art was granted in November last year.
A planning statement prepared on behalf of the council said: “Currently, the site is in a state of dilapidation.
“The walls are stained due to water ingress from the railway structure above, lighting has been subject to vandalism, and the area is widely perceived as unsafe.
“Upon reopening, the space will present a dramatically transformed environment for public use.”