Thousands of years back the capital of the whole, world empire was present Delhi. It was called Hastināpura or Gajasāhvaya. Gaja and hasti means elephant. There would have been many elephants because formerly the kings used to keep many horses, elephants. Even now in New Delhi they have kept some token elephants in front of Indian President’s house. So formerly there was one king, and the capital was Hastināpura. The king of Hastināpura was ruling all over the world. There was one flag. There were not many states, and the world was under one culture, Vedic culture.These are mentioned in the Śrīmad-Bhāgavatam.
The advanced people were called Aryans. Arya means advanced in culture and education. The Indo-European stock are also Aryans. They came from Central India, Central Asia, and some of them went to Indian side. This is the history. The Caspian sea was the place of Kaśyapa Muni. From the word Kaśyapa the Caspian has come. Just like formerly the capital of Afghanistan was known as Gandhar. Now it has become Kandahar. So by historical references, it can be ascertained that the whole planet was known as Bhāratavarṣa. Presently only India is now known as Bhāratavarṣa, but formerly the whole planet was known as Bhāratavarṣa. Much before this planet was known as Ilāvṛtavarṣa, but since the time of King Bharata – the forefathers of the Pāṇḍavas, the planet is called Bhāratavarṣa. Just like nowadays we say “greater India,” greater some city, “greater New York,” so this Mahābhārata means History of the greater Bhāratavarṣa.
So Hastināpura was capital, and the king of Hastināpura was the emperor of the world. There were other states also, but they were paying tax to the emperor.
Ref >> Srila Prabhupada Vani.