Before 680 CE the site of Karbala was open desert on the edge of the Euphrates floodplain, without the standing that later made it one of the most visited cities in the Islamic world. A settlement grew up around the graves of Husayn and al-Abbas gradually over the following centuries, its fortunes tracking the shrine's own, expanding under periods of tolerant rule and shrinking when the shrine itself was attacked or its pilgrimage suppressed. That pattern, a city whose population and economy scale directly with its shrine's standing, is one Karbala shares closely with Najaf and Qom, though its urban core is more compact and more completely organized around the two shrine compounds at its center than either.
Karbala is today the capital of Karbala Governorate in south central Iraq, with a resident population that has grown substantially in recent decades alongside its pilgrimage economy, which now accounts for a large share of local employment through hotels, transport, food service and religious goods. The city's infrastructure, built to serve a population many times its permanent residents during Ashura and Arbaeen, gives it an unusual seasonal rhythm: quieter for much of the year, and overwhelmed for a period of weeks around the fortieth day after Ashura.