Which Roman building has the world’s largest unsupported concrete dome?

Here is the question :

WHICH ROMAN BUILDING HAS THE WORLD’S LARGEST UNSUPPORTED CONCRETE DOME?

Here is the option for the question :

Colosseum
Pantheon
Library of Celsus
Capua Amphitheater

The Answer:

And, the answer for the the question is :

PANTHEON

Explanation:

[STC0013621]. Even today, the Pantheon is a testament to engineering brilliance. It was finished around 128 CE and rests on top of an older structure. It is a 142-foot-diameter concrete and brick dome that stands 71 feet tall. No one knows for sure how it was constructed, but it has served as an inspiration for many other buildings, notably the United States Capitol.