An architectural and engineering marvel is silently standing within a public building in the old town of Graz. Completed in 1438 under the guidance of Holy Roman Emperor Frederick III, the Burg of Graz was expanded by Frederick’s son, Emperor Maximilian, from 1494-1500. When reopened, officials and civilians marveled at the Doppelwendeltreppe, or “Double Spiral Staircase” that traveled two floors to the top of the tower.

The staircase splits and rejoins several times as it circles upward to the top, and has often been interpreted as a symbol of eternity. Graz people call it the “stairs of reconciliation” for if you go separate ways, you will ultimately reunite.

Built by an unknown architect, the staircase has proven to stand the test of time, and feet, as the Burg is still used for official town purposes today.

Double spiral staircases are not unheard of, though they are very rare. This one is remarkable for hollow spindles, which feature a remarkable amount of dexterity in engineering.

The sister staircase of this one was built 50 years prior in Elisabeth Cathedral in Košice, Slovakia, but lacks the grandeur and sophistication of its successor.