Hidden tunnel and rooms unearthed under 1,500-year-old church in Istanbul

Here we see an underground chamber with brick-lined walls.

Archaeologists excavating beneath the ruins of an early Christian church have unearthed underground rooms and a tunnel from 1,500 years ago in the oldest part of Istanbul — once Constantinople, the capital of the Byzantine Empire.

The purpose of the hidden structures isn't completely understood, but they are probably part of the vast Church of St. Polyeuctus above them, which was built when the city was the center of Christianity, the empire's official religion.