Centennial Hall in Wrocław

You're standing at the Hala Stulecia, Wrocław's Centennial Hall. From outside it might look like a grey concrete dome, but this building made architectural history. When it was completed in 1913, it was the largest reinforced concrete structure of its kind. Architect Max Berg, then head of the city's building department, took inspiration from the Pantheon in Rome. Since 2006 the hall has been a UNESCO World Heritage Site.