The early Roman civilization developed over three major periods - the Roman Monarchy, Republic, and Empire. During the Monarchy, Rome was ruled by kings and had a senate of nobles and two main social classes, patricians and plebeians. The Republic saw the rise of consuls, a stronger senate, and the plebeians gaining more rights. The Empire began when Augustus Caesar rose to power, transforming Rome into a vast empire with an autocratic government stretched across Europe and around the Mediterranean. Roman innovations included advanced architecture like aqueducts and domes, roads and infrastructure, as well as baths, art, literature, and an urban grid plan model for cities.