The viaduct's 13 segmental arches carry it across the valley of the Dollis Brook, and over Dollis Road. Each arch spans at the springer level, and is based on tapered piers. In each pier there is an opening with an arched soffit and a dished invert. The viaduct is made from brick. It is the highest point on both the Northern line and the highest point on the London Underground above ground level, reaching nearly . It is not, however, the highest altitude on the Underground system, which is near Amersham (Metropolitan line) in the Chiltern Hills, at above sea level.