Secret imperial tunnel beneath Rome’s Colosseum will open to the public On October 27, Rome’s Colosseum will open the Passage of Emperor Commodus to the public for the first time in nearly 2,000 years. This newly restored underground corridor once allowed Roman emperors to enter the arena unseen, leading directly to the imperial box overlooking the games. Archaeologists say the tunnel, rich with frescoes and marble, was built between the reigns of Domitian and Trajan, and later named after Commo