10th century Since I was a kid, I have always been a fan of the graphic art of Dutch illustrator Maurits Cornelis Escher. 
He is probably most famous for his optical illusions, like his drawing of the never-ending-staircase or the impossible waterfall,
but his impossible triangle is probably one of the easiest to draw (if impossible to make!), so I started with this!
This is a vector graphic, drawn entirely using Adobe Illustrator.