The Apostle Paul came to Philippi on his second preaching journey. Luke accurately describes the city with these words:
So putting out to sea from Troas, we ran a straight course to Samothrace, and on the day following to Neapolis; and from there to Philippi, which is a leading city of the district of Macedonia, a Roman colony; and we were staying in this city for some days. (Act 16:11-12 NAU)
The photo below shows ruins of the theater which was cut into the mountain side. It was built in the days of Philip II in the 4th century B.C. During renovations in the second and third century A.D. arrangements were made for gladiatorial contests.
According to Fant and Reddish,
the theater was modified for gladiatorial contests. The first three or four rows of seats were removed, protective walls were added to keep the animals from the audience, new rows of seats were added on the upper part of the theater, and, in the 3rd century, an underground tunnel was constructed underneath the orchestra for the purpose of bringing in the wild animals. (A Guide to Biblical Sites in Greece and Turkey, 109-110)