The ancient Roman Empire spread not just throughout much of what is today western Europe, but east, as well, including present day Romania and the Balkans (including Bulgaria). In 188 BCE the Romans invaded the region of Thrace (covering southeastern Bulgaria, northeastern Greece, and the European part of Turkey), finally conquered it in 46 CE and ruling until the empire began falling apart in the mid 5th century and Germanic tribes took over. Its capital was the city of Philippolis, in 342 BCE founded by and named after Phillip the Great, ruler of the ancient Greek kingdom of Macedonia (and father of Alexander the Great), making Bulgaria´s second largest city Plovdiv (pop. 372,000) one of Europe´s oldest continuouslay inhabited cities.  And the legacy left by the Romans can still be seen today, are easily explorable on foot. And to help you understand what you´re seeing, you can opt for human guides or audio guides which provide expertly crafted, detailed explanations of history interspersed with interesting anecdotes and enriching lesser known facts. The advantage of human guides includes being able to ask specific questions, while the audio option allows you to move at your own pace. 

Read more in Tripatini contributor Simon Hopes´ post The Compelling Roman Ruins of Plovdiv, Bulgaria.