Riddarholmsbron (Riddarholm Bridge), Stockholm

The Riddarholm Bridge (Riddarholmsbron) is a historic bridge in Stockholm, connecting the islets of Stadsholmen and Riddarholmen in Gamla Stan, the city's old town. Originally constructed in 1630 as a wooden drawbridge by Councillor Åke Tott, it was designed to accommodate both pedestrian and horse traffic. This early version of the bridge played a crucial role in linking important parts of the city, reflecting the needs and technologies of the time.

In 1784, the wooden bridge was reconstructed using stone, with a high arch designed by architect Erik Palmstedt to allow boats to pass underneath and to support the passage of carriages, including those of the Royal Family and the nobility. Despite its sturdy construction, this version of the bridge lasted less than a century.

In 1867, the bridge was demolished to make way for the railroad, as the need for stronger materials led to the use of cast iron to withstand the weight and stress of locomotives. During this reconstruction, architect Ragnar Östberg had the innovative idea to preserve a piece of the bridge's history by relocating Palmstedt's stone vault to the gardens at Stockholm City Hall, where it became known as Palmstedt Grotta, or "Cave of Palmstedt."

The Riddarholm Bridge underwent its most recent transformation in the 1950s, reflecting the evolving demands of modern transportation. The stone and cast iron bridge was replaced with a closed-frame concrete bridge to support the growing volume of automobile traffic.