The story is set during the historically real Mongol invasion of the Russian principalities under Batu Khan, grandson of Genghis Khan, beginning in 1237–1238 — a genuine catastrophe that destroyed Vladimir and numerous other cities and marked the start of over two centuries of Mongol dominance over Russian lands. Within this real historical backdrop, the Kitezh legend inserts a specifically fictional episode: after Batu's forces capture Lesser Kitezh, Prince Georgy retreats to Bolshoy Kitezh, whose location deep in the forest by Lake Svetloyar remains hidden. Mongol torture eventually extracts the secret path from a captive, and Batu's army arrives to find a city with no walls, no soldiers, and no intention of fighting — only prayer.
The specific miracle differs slightly between tellings, but the outcome is constant: the city vanishes beneath the lake rather than being taken, and the last image the attackers see is its golden domes disappearing beneath the water. In some versions of the legend, the city did not exactly sink so much as become invisible, and the lake itself is described as offering a kind of window onto Kitezh for those spiritually prepared to see through it.