The first senate was that of the Roman Republic. The Senate was the dominant force in the politics of the Roman Republic. The Roman Senate consisted of 300 senators who met in the Curia or Senate house.
The Senate of the later Roman Republic was increased to over a thousand members by Julius Caesar. When the Roman Empire began under the first Emperor, Augustus, the Senate still had influence, although the Emperor was the supreme head of state. By the 2nd century A.D., the Senate became more of a figurehead body subject to the orders of the Emperor. In the late 3rd and 4th century, it had become completely powerless with most of its powers stripped away. Senators were prevented from taking up Military Commands and they lost the legal right to appoint and give consent to the powers of Roman Emperors.