What was the greatest empire ever?

In my suggestion Rome is the world's biggest empire in the world. Rome is the capital of Italy and the country's largest and most populated municipality The city of Rome is located in the central-western portion of the Italian Peninsula. Rome's history spans over two and half thousand years. It was the capital city of the Roman Kingdom in the eighth century it became the capital of the Papal States, which lasted until 1870. In 1871 Rome became the capital of the Kingdom of Italy.