It's the site of the Imam Hussein shrine, one of Shiite Islam's holiest locations.

CNN: Death toll rises to 50 in Iraq bombing

According to historical accounts, Imam Hussein was killed in a battle near Karbala, where he was overwhelmingly outnumbered by Yazeed's army.

CNN: Pilgrims flood Karbala on final holy day

Karbala is where Muslim martyr Imam Hussein bin Ali -- grandson of the prophet Mohammed -- was killed and entombed more than 1, 300 years ago.

CNN: Pilgrims flood Karbala on final holy day

The holy day commemorates the end of a 40-day mourning period for Imam Hussein, the grandson of the Prophet Mohammed and one of the most revered Shiite figures.

CNN: Women, children among 38 killed near Iraq festival

Police initially blamed Shiite pilgrims trying to push past frustratingly slow security checkpoints near the Imam al-Hussein mosque.

NPR: Clashes in Karbala Force Pilgrims to Flee