Revelation3chapter 3

Sardis had been the capital of the fabulously rich Lydian kings, and its citadel sat on a spur of rock people called unassailable. It was taken twice — by the Persians under Cyrus and later by Antiochus III — both times by a climber finding a way up at night while the defenders slept, confident nobody could come that way. "If therefore thou shalt not watch, I will come on thee as a thief" is that story handed back to the city.

Sardis was also a wool and dyeing town, which gives edge to the promise of a few who "have not defiled their garments" and shall walk in white.

Philadelphia sat in earthquake country. A massive quake in AD 17 flattened it and Sardis, and Philadelphia kept suffering aftershocks so badly that people camped outside the walls rather than sleep under a roof. To that church: "him that overcometh will I make a pillar in the temple of my God, and he shall go no more out." A pillar that never falls, in a city where nothing stayed standing.

Laodicea was rich — a banking center that, after an earthquake around AD 60, rebuilt itself without imperial help, which the Roman historian Tacitus records. It was known for glossy black wool and for a medical school associated with an eye treatment.

And Laodicea had bad water. Its neighbors had the famous hot mineral springs at Hierapolis and cold, fresh streams at Colossae. Laodicea's water was piped in, and it arrived neither hot nor cold — lukewarm and mineral-heavy enough to make you spit it out. Every image in that letter is a Laodicean specialty turned inside out: buy of me gold tried in the fire, white raiment instead of your black cloth, eyesalve that actually works.