While the basics of stadium design have
changed very little since the Colosseum of ancient Rome - concentric
corridor under seats with spectator distribution inwards to the
different seating tiers - their aesthetics has changed dramatically.
Lightweight steel structures have given way to longer spans and
greater coverage and slick, modern designs. Subsequently, the
roof has become important as the "fifth facade", especially
to the home viewers seeing a stadium from the hovering blimp.
In Beijing, the architects provided an irregular, oblong opening
with a retractable roof, enabling games in inclement weather.
