considered among the greatest houses of worship in both the Christian and Muslim

worlds:

Hagia Sophia, the Great Church of Constantinople.

Built by the Byzantine Emperor Justinian in the early 6th century on the grandest

scale possible, it was later converted into a mosque by the conquering Ottomans.

Today

it's a museum.

Hagia Sophia, which marks the high point of Byzantine architecture

is the pinnacle of that society's 6th century glory days.

This church was completed in 537,

just about when Europe was entering its Dark Ages.

For four centuries after that, Christians in Europe looked to Constantinople as the leading

city in Christendom

and this was its leading church.

This clever dome-upon-dome construction was the biggest dome

anywhere until the cathedral of Florence was finished during the Renaissance

900 years later.

The vast interior gives the impression of a golden weightless shell,

gracefully disguising the massive overhead load

supported by masterful Byzantine engineering.

Forty arched windows shed a soft light on the interior, showing off the church's

original marble and glittering mosaics.

But the Byzantine Empire collapsed in the 15th century, and Hagia Sophia

was turned into a mosque. Christian mosaics were plastered over, and new

religious symbols replaced the old.

This church was built to face Jerusalem;

mosques face Mecca.

When Hagia Sophia became a mosque, they couldn't move the church, but they could move

the focal point of the praying. Notice how the prayer niche is just

a little bit off-center.

That's because it faces Mecca.