Laodicea on the Lycus was an ancient city built on the river Lycus (Çürüksu). It was located in the Hellenistic regions of Caria and Lydia, which later became the Roman Province of Phrygia Pacatiana. It is now situated near the modern city of Denizli, Turkey. In 2013 the archaeological site was inscribed in the Tentative list of World Heritage Sites in Turkey. It contained one of the Seven churches of Asia mentioned in the Book of Revelation.
Laodicea is situated on the long spur of a hill between the narrow valleys of the small rivers Asopus and Caprus, which discharge their waters into the Lycus. The town was originally called Diospolis, "City of Zeus", and afterwards Rhodas. Laodicea, the building of which is ascribed to Antiochus II Theos in 261-253 BC in honor of his wife Laodice, was probably founded on the site of the older town. It was approximately 17 kilometres (11 mi) west of Colossae, and 10 kilometres (6.2 mi) south of Hierapolis. It was approximately 160 kilometres (99 mi) east of Ephesus and, according to Strabo, it was on a major road. It was in Phrygia, although some ancient authors place Laodicea in differing provincial territories – not surprising because the precise limits of these territories were both ill-defined and inconstant; for example, Ptolemy and Philostratus call it a town of Caria, while Stephanus of Byzantium describes it as belonging to Lydia.
At first, Laodicea was not a place of much importance, but it soon acquired a high degree of prosperity. In 220 BC, Achaeus was its king. In 188 BC, the city passed to the Kingdom of Pergamon, and after 133 BC it fell under Roman control. It suffered greatly during the Mithridatic Wars but quickly recovered under the dominion of Rome. Towards the end of the Roman Republic and under the first emperors, Laodicea, benefiting from its advantageous position on a trade route, became one of the most important and flourishing commercial cities of Asia Minor, in which large money transactions and an extensive trade in black wool were carried on.
The area often suffered from earthquakes, especially from the great shock that occurred in the reign of Nero (60 AD) in which the town was completely destroyed. But the inhabitants declined imperial assistance to rebuild the city and restored it from their own means. The wealth of its inhabitants created among them a taste for the arts of the Greeks, as is manifest from its ruins, and that it contributed to the advancement of science and literature is attested by the names of the sceptics Antiochus and Theiodas, the successors of Aenesidemus and by the existence of a great medical school. Its wealthy citizens embellished Laodicea with beautiful monuments. One of the chief of these citizens, Polemon, became King of Armenian Pontus (called after him "Polemoniacus") and of the coast round Trebizond. The city minted its own coins, the inscriptions of which show evidence of the worship of Zeus, Æsculapius, Apollo, and the emperors.
It received from Rome the title of free city. During the Roman period, Laodicea was the chief city of a Roman conventus, which comprised twenty-four cities besides itself; Cicero records holding assizes there ca. 50 BC.
Antiochus the Great transported 2,000 Jewish families to Phrygia from Babylonia. Many of Laodicea's inhabitants were Jews, and Cicero records that Flaccus confiscated the considerable sum of 9 kilograms (20 lb) of gold which was being sent annually to Jerusalem for the Temple (Pro Flacco 28-68). The martyrdom of Lulianos and Paphos is believed to have happened here.
The Byzantine writers often mention Laodicea, especially in the time of the Comneni. In 1119, Emperor John the Beautiful and his lead military aid John Axuch captured Laodicea from the Seljuk Turks in the first major military victory of his reign.
It was fortified by the emperor Manuel I Comnenus. In 1206–1230, it was ruled by Manuel Maurozomes. The city was destroyed during the invasions of the Turks and Mongols.