In what ways was the advent of the arch an important milestone for Roman technology?

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)

the foundation of greek city-states: following the fall of the mycenaean civilization in the 10th century bc, the area surrounding the empire went through its own mini dark ages. answer and explanation