This is a swing door (hence there is no door handle) leading from a conservatory down to a garage. It was painted in two days and gives the illusion of stairs going upwards.
There appears to be an alcove in the wall with a bottle of the customers favourite drink in it. The floor in the painting does actually match the floor of the conservatory in real life but it doesn't show it in this flash photo.
The finished mural was varnished with several coats of matt varnish for extra protection.