was an Italic civilization
that began on the Italian Peninsula
as early as the 8th century BC. Located along the Mediterranean Sea
and centered on the city of Rome
, it expanded to become one of the largest empires
in the ancient world
with an estimated 50 to 90 million inhabitants (roughly 20% of the world's population) and covering 6.5 million square kilometers (2.5 million sq mi) during its height between the first and second centuries AD.