One Great George Street (OGGS) is a four-domed grade II listed Edwardian building used as a conference and wedding venue just off Parliament Square in Westminster, London, England.

The exterior, foyer and staircase are made of Portland stone and many of the rooms are ornately decorated with French walnut and oak panelling, carved plaster ceilings and elaborate crystal chandeliers.

The walls of the Great Hall can be described as a 'Graeco-Roman rhapsody', as huge marble pilasters with bronze effect Ionic capitals and metal bases interspersed with consoled panels that frame portraits from the Institution's oil paintings collection flow around the vertical surfaces.

The ceiling of the Great Hall features a huge painting by Charles Sims commemorating World War 1 (the patron being Sir John Purser Griffith, ICE President in 1920).

Peering down at the viewer from the edge of the painting are servicemen and women dressed in uniforms reflecting the different branches of the military and above them can be seen a low-flying biplane with fixed undercarriage proudly displaying its red, white, and blue insignia.

The Telford Theatre also holds a twin fusee Grand Sonnerie Bracket Clock made by the famous clockmaker Thomas Tompion, who is buried in Westminster Abbey.