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

Overview
Sergels torg has a dominant west-to-east axis and is divided into three distinct parts.
A sunken pedestrian plaza furnished with a triangular pattern (colloquially referred to as Plattan, "The Slab") and a wide flight of stairs leading up to the pedestrian street Drottninggatan, connecting south to Stockholm Old Town and north to Kungsgatan.
This plaza is partly overbuilt by a roundabout centred on a glass obelisk and by the concrete decks of three major streets.