These 27 white crosses to the east of the Old Town City Hall form a memorial for the 27 Czech Protestant noblemen executed here in 1621 for their role in the 1618 Defenestration, during which they threw two Vienna appointed Catholic governors out a window of the Prague Castle and elected their own king. Their revolt for religious freedom was short-lived, as their Bohemian army was defeated by a superior Hapsburg Imperial force at the Battle of White Mountain (Bílá Hora) in 1620. This marked the beginning of the Thirty Years' War, which was fought throughout Europe. Bohemia was devastated by this war and the Jesuit led Counter-Reformation.

Incidentally, the two Catholic governors survived the Defenestration, not because angels kept their “feet from striking on stones”, but their 70-feet falls were cushioned by a large pile of manure.