Plovdiv is the second-largest city in Bulgaria after Sofia with a population of 338,153 inhabitants according to Census 2011. Plovdiv's history spans some 6,000 years, with traces of a Neolithic settlement dating to roughly 4000 BC. Some sources include Plovdiv among Europe’s oldest continuously inhabited cities. It is the administrative center of Plovdiv Province in southern Bulgaria and three municipalities (Plovdiv-city, Maritsa and Rodopi) and Bulgaria's Yuzhen tsentralen planning region (NUTS II), as well as the largest and most important city in Northern Thrace and the wider international historical region of Thrace. The city is an important economic, transport, cultural and educational center. The oldest American educational institution outside the United States was founded in Plovdiv in 1860, it was later moved to Sofia – today’s American College of Sofia.
Known in the West for most of its history by the Greek name Philippopolis, it was originally a Thracian settlement before becoming a major Roman city. In the Middle Ages, it retained its strategic regional importance, changing hands between the Byzantine and Bulgarian Empires. It came under Ottoman rule in the 14th century. In 1878, Plovdiv was made the capital of the autonomous Ottoman region of Eastern Rumelia; in 1885, it became part of Bulgaria with the unification of that region and the Principality of Bulgaria.
Plovdiv is situated in the southern part of the Plovdiv Plain on the two banks of the Maritsa River. The city has historically developed on seven syenite hills, some of which are 250 m (820.21 ft) high. Because of these seven hills, Plovdiv is often referred to in Bulgaria as "The City of the Seven Hills".
Plovdiv is host to economic and cultural events such as the International Fair Plovdiv, the international theatrical festival "A stage on a crossroad", the TV festival "The golden chest". There are many remains preserved from Antiquity such as the Ancient amphitheatre, Roman odeon, Roman Stadium, the archaeological complex Eirene and others.
Plovdiv has 20 sister cities.