Double spiral staircase, an architectural and engineering marvel of its time at Burg de Graz Castle in Austria. Completed in 1438, under the direction of Roman Emperor Frederick III, Burg de Graz was extended by Frederick's son, Emperor Maximilian from 1494-1500 EC. When they reopened their doors, officials and civilians alike marveled at the "Doppelwendeltreppe", or "Double Spiral Staircase", which runs through two floors to the top of the tower. This architectural masterpiece has often been interpreted as a symbol of eternity. People call it "reconciliation stairs". If you part, you will reunite at some point.
