I was watching a Crash Course World History video, and right here you are briefly shown a map. It got me thinking about what existed east of easternmost Rome. In my mind there's Rome in the "west" and somewhere over to the east you eventually run into "India" and "China"* but that's obviously a gross oversimplification. So what was there in the middle/in those eastern white spaces on the map?
Secondly, is that map even all that accurate? This map taken from [here] (http://en.wikipedia.org/wiki/Campaign_history_of_the_Roman_military#Empire), looks fairly similar but the article says Roman Assyrian only existed for 2 years.
*Quotation marks because I don't know how unified these areas were.
TL;DR: What was between Rome and China? How far east did Rome go?
The area of what is today Irak/Iran had its own great empires throughout ancient history. At the time of the Greek city states (when Rome was still a small city in Italy) there was the Achaemenid (or Persian) Empire. The struggle between the Greeks and the Persian Empire defined much of Greek history of that time. The Battle of Marathon was fought when the Persians under Darius the Great invaded Greece and the Battle of Thermopylae (of "300" fame) was fought when Xerxes I invaded Greece. The mighty Persian Empire failed to conquer the Greeks though and in the end the tables were turned on them. In the 330s BC, Alexander the Great led a Macedonian-Greek army in repeated victories against Persian forces, bringing the Persian Empire to an end.
Alexander took over the Persian empire and expanded it, but his empire was short-lived. After Alexander's sudden death the empire fell into a few (still quite significant) pieces. The part in what is now Irak/Iran became the Seleucid Empire. That empire expanded westward into Syria. This is when the Romans first came into military contact with the Seleucids, which is why they're often referred to as 'Syrian'.
In the early 2nd century BC, Rome was starting to get involved in Greece from the west. At the same time the Seleucids were also spreading their influence there from the east. At the same time the power of Macedon, which lies just north of Greece and between Rome and the Seleucid Empire, was declining. In 191 BC Seleucid king Antiochus III moved his forces into Greece to put an end to Roman influence there. The Romans sent their own army to Greece and the forces came to blows at Thermopylae (the very site of the Greek battle against the Persians some 3 centuries earlier). The result was an overwhelming Roman victory. Antiochus III had to accept a humiliating peace which among other things meant that the Seleucid Empire would stay out of Asia Minor (modern-day Turkey).
From here on the Seleucid Empire slowly declined, until it was finally finished off by Pompey in the first century BC. This was not due to the Romans alone though. While the Seleucids were involved with Rome at their western border, in the east another power was rising. Parthia was a break-away region of the Seleucid Empire (near modern-day Turkmenistan) which grew in power and started chipping away at the Seleucid Empire from the east. From the mid-first century BC the Roman Empire and the Parthian Empire shared a border. After Crassus' catastropic defeat at the hands of the Parthians in 53 BC the Romans were reluctant to get too involved with the Parthians. Both empires saw periods of conflict (around Armenia especially) and peace, but neither was powerful enough to defeat the other. This is the period of the map your question is about. So at the time of that map, all that was between Rome and India was the Parthian Empire.
The Parthian Empire eventually was replaced by the Sassanid Empire in the third century AD. The Sassanids too were in regular conflict with the Romans, even managing to snatch some territory from the Eastern Roman Empire.
So here's your answer of what was east of Rome: for over a millenium it was a series of large empires spanning mostly from the Mediterranean to India, each very interesting and each largely ignored in western histories apart from battles with Greece or Rome:
The Roman Empire expanded its furthest eastwards between AD 115-117, during Trajan's Parthian War, in which Rome temporarily conquered the territories that were referred to as the provinces of Armenia, Mesopotamia and Assyria.
Obviously, the Parthians were immediately east of Rome, but beyond them, in modern day Afghanistan, Pakistan, and North western India, was the Kushan Empire, which controlled the Silk routes between Parthia and Rome in the West, and China (under the Han Dynasty) in the East.
