Erfurt Latrine Disaster

This article covers the Erfurt Latrine Disaster, which occurred on July 26, 1184, in Erfurt, Germany. During a meeting with local nobility, the floor of a building collapsed under the weight of the attendees, sending them into the latrine cesspit below. Around sixty people passed, with some tragically drowning in the waste.
#6 Actually a really cool list
#19 I remember when I first found out that the Roman statues used to be paint to make them appear lifelike. Creepy.