Chicago's United Center has seen its share of world-class performances. Its decision to ditch plastic water bottles may be the most important one yet. 

At the beginning of September, recyclable aluminum bottles officially replaced all plastic water bottles at concession stands, in locker rooms, and in stadium boxes. Filtered water fountains were added around the arena — including some sparkling water ones — and there are nearly 100 new recycling bins so visitors can easily recycle their aluminum bottles if they don't want to take them home.

The arena hosts over 200 major events every year, from basketball and hockey games to concerts to the recent Democratic National Convention. In a world of “everyone can do one small thing,” this could be a big one. Surely, other arenas and stadiums worldwide will keep an eye on this.