Rome: A vast underground passageway that allowed Rome’s emperors to pass unseen from their hilltop palaces to the Forum will open to the public for the first time Wednesday.

The 2,000-year-old “imperial ramp” descended from the top of the Palatine Hill to the temples, market places and courts of the Forum below, from where the Roman Empire was governed.

Lit by torches and protected by guards, the passageway, with 36ft-high ceilings, was so vast that emperors could have comfortably passed through it on horseback.

Originally more than 300 yards long, it consisted of seven zigzag ramps, four of which remain today.

The rest are believed to have been destroyed in an earthquake in the ninth century AD. The tunnel was first discovered in 1900. It was partially excavated but then abandoned for another century, until archaeologists embarked on a major restoration project a few years ago.