Gérard Michel is a Belgian architect based in Liége, who also teaches courses in sketching and drawing at the school of architecture there.
He sketches in pencil, pigment liners and watercolor.
In keeping with his background, Michel excels at rendering buildings and architectural forms and evidences a fascination with them. He has a wonderful knack, however, for leaving parts of his drawings open and sketch-like, even though they can be very exacting in their proportions and perspective.
He has been posting hundreds of his wonderful sketches from his sketchbooks, both of his home city of Liége and his travels elsewhere, to his Flickr stream. You can get a quicker overview by looking through his Urban Sketchers posts, but the Flickr sets are well worth exploring.
There is a brief clip of him sketching on Vimeo.