The Aegean Sea (supplemented by the resistance of the southern city-states of mainland Greece to Persian takeover).
The landform that stopped the Persian Empire from spreading north was the Caucasus Mountains. The rugged terrain and harsh climate of the Caucasus made it difficult for the Persians to conquer territories beyond this natural barrier.
The Aegean Sea (supplemented by the resistance of the southern city-states of mainland Greece to Persian takeover).
The Byzantine Empire was to the north and northwest of Arabia while the Persian Empire was to the north and northeast of Arabia.
The Himalayan Mountains stopped the Roman and Chinese empires from spreading north.
Cyrus the Great.
The Persian Empire was established in Asia, North Africa and Eastern Europe. That makes three continents. Your other four continents were not involved.
By conquering peoples stretching from North Africa to Central Asia and integrating them into the empire and using their resources.
Persia itself is now Iran. The Persian Empire embraced many present countries in North Africa, the Middle East, Central Asia and Pakistan.
The Persian Empire had access to several bodies of water, including the Persian Gulf to the south, the Caspian Sea to the north, the Mediterranean Sea to the west, and various rivers such as the Tigris and Euphrates in Mesopotamia. These bodies of water played a significant role in trade, transportation, and agriculture within the empire.
Improvements in stability, peace and prosperity in southern Asia and north Africa for two centuries.
He absorbed Media into partnership. This was not an empire. The empire came later when they expanded through Central Asia, the rest of the Middle East and North Africa.
He took over the Empire pretty much as it was. His attempts to extend it in the east to India appear to have failed, and his plans to extend it in Europe and North Africa were curtailed by his death.