Centennial Hall in Wrocław

Concrete had never done anything like this. Max Berg's Centennial Hall, raised in Wrocław's exhibition grounds in 1911–1913, spans a vast circular space seating about 6,000 beneath a ribbed dome 23 m high, crowned by a steel-and-glass lantern — a symmetrical quatrefoil that rewrote what reinforced concrete could achieve and shaped the structures that followed. UNESCO inscribed this engineering landmark in 2006.