At the main entrance to the San Giovanni in Laterano - the Cathedral of Rome, founded by Emperor Constantine in the early 4th century.
Since its foundation predates that of St. Peter by 14 years, it is therefore considered as the oldest Christian basilica in the world.

On Maundy Thursday the Pope, as Bishop of Rome, gives a blessing from the loggia (see top left) of the city's main cathedral.
Newly-elected Popes are formally inaugurated/introduced here.