The Tharabha Gate into Old Bagan, built in the 9th century
In 847, King Pyinba erected a wall around the city of Bagan. This was a few hundred years before Bagan's "golden age" when most of the large temples and pagodas were built, which explains why many of the sights are outside of the walls.
The remains of the moat outside the city wall
Of the twelve or so original gates, only the eastern Tharabha Gate remains, and it in fact has been reconstructed. While the gates are solidly built of brick, the rest of the city walls were mostly built with mounds of earth and rubble.
The gate is flanked by two niches housing statues of Bagan's guardian spirits (nats), a brother and sister team called Min Maha Giri.