Laodicea was a city 40 miles southeast of Philadelphia and 80 miles east of Ephesus in western Asia Minor (Turkey). It was a wealthy city with a renowned medical school. It exported fine woolen garments and was famous for its eye salves.
Laodicea did not have adequate water, and water from the hot springs 6 miles south was piped in via an aqueduct, and when it reached the city, the water was lukewarm. The letter to the church of Laodicea is the 7th written to the 7 churches in Revelation, chapters 2 and 3. Christ rebukes the church in Laodicea as being neither hot nor cold, but lukewarm (like the water).
He rebukes them for being rich and affluent and having no need for anything, yet they do not realize they are wretched, pitiable, poor, blind and naked. Laodicea was cautioned to recognize that despite its financial prosperity, it was impoverished and in need of spiritual riches. The original site of Laodicea is now abandoned, but the ruins of a Roman aqueduct are still there.
The other six churches that are mentioned in this part of the book of Revelation are Ephesus, Pergamos, Philadelphia, Sardis, Smyrna, and Thyatira.