The Senate and People of Rome.
From where we are spending a couple of nights it’s a 3 euro & 20 minute train ride to the center of Rome. On the one hand it would be a shame to be 20 minutes from Rome and not visit the collosseum and forum. On the other hand, the center of Rome was flooded with tourists and far more crowded than on our other visits in years past, making for a less interesting visit. We hopped back on the train after a walk around the colosseum and forum.
As the stadium is made of marble, the Italian authorities have brought in a gigantic marble-making machine. They should have no problems maintaining a supply of marbles sufficient to complete the stadium.