Traditional masonry is rare. Chances are that when you see a stone or brick building, there is a steel frame underneath that’s doing most of the heavy lifting. In the days before steel, all those heavy materials were supported by thick, load-bearing walls.

When it was built in 1901, Philadelphia City Hall was the tallest skyscraper in the world, the first non-religious building to hold the title. At 548 feet high, it remains the world’s tallest load-bearing building.

The load-bearing walls of this architectural wonder are 22 feet thick in some places, allowing them to support the heavy masonry work above. Construction took 30 years to complete and cost a total of 24 million dollars. After its construction, no architect had the desire to attempt such an ambitious project.

Philadelphia’s City Hall remains one of the most impressive buildings we’ve seen.