Mind Your Step Illusion By Erik Johansson, Sergel's Square, Stockholm, Sweden

History
Before the creation of Sergels torg, Brunkebergstorg was the most important public space in the area, the hub about which traffic revolved, the place where people would go to work and to find entertainment.
• Early proposals
Albert Lilienberg was appointed city-planning superintendent in 1927, and a year later he produced the first proposal for a public square on the location in his general plan of 1928. In his proposal he envisioned a square whose north-south oriented axis would line-up with Sveavägen intended to be extended south across the square down to the waterfront with widened Hamngatan and Klarabergsgatan joining in from west and east. After this first proposal, the square is featured on every subsequent city plan produced for the area, with alternations in width and length. Notwithstanding the considerable number of revised proposals produced, surprisingly few were preoccupied by architectonic considerations, instead focusing on optimization of traffic flow.