The sheer scale of the Volkshalle led to several theoretical engineering issues that might have made its completion impossible:

A diameter of 250 meters, large enough to fit several St. Peter’s Basilicas inside.

The Volkshalle was intended to serve as a secular "cathedral" for the Nazi regime, symbolizing the permanence and power of the "Thousand-Year Reich". It was to be situated at the northern end of a three-mile-long "Avenue of Splendors". Engineering and Environmental Challenges

The project was a collaboration between Hitler and his chief architect, Albert Speer . It was intended to be the largest domed building in the world, inspired by the Pantheon in Rome but built on a scale that would dwarf it. Nearly 290–300 meters.

Designed to hold between 150,000 and 180,000 people for rallies and speeches.

Planned to be constructed primarily from massive amounts of granite. Historical and Symbolic Intent