The horizon frequently features vanishing points of lines appearing parallel in the foreground. (en.wikipedia.org)
Indeed, Grotjahn's early work established his capabilities as a skilled draughtsman, from the Sign Replacement Project that involved him making careful copies of shop signs and trading them for the originals, to his abstract experiments with multiple vanishing points in the late 1990s. (christies.com)
Through his oil paintings, pencil and cardboard works and sculpture, Mark started to experiment with the perspective often employing multiple vanishing points in his museum and gallery work and it's at this time that Grotjahn started getting noticed for his unique art. (widewalls.ch)