english: To make it even structurally possible, they had to invent super-strong concrete, and to control weight, varied the density of the aggregate as they worked their way up the dome.
non_english: Da je bila gradnja sploh strukturno mogoča, so morali iznajti super-močen beton in za nadzor teže prilagajati gostoto agregata, ob vzpenjanju s kupolo navzgor.