Tong Vey

From Memory Alpha, the free Star Trek reference.

Tong Vey is a historic Klingon city in which a group of warriors, after winning a great victory, were ordered by Emperor Sompek to slaughter every last villager and burn the city to the ground.

Worf was fond of a holo-program that recreated the Battle of Tong Vey. This came back to haunt him later when Ch'Pok brought it up at his trial. (DS9: "Rules of Engagement")