During the Second World War, water reservoirs were built at public places in Prague to supply water in case of fire caused by air raid attacks. Zdeněk Wirth named a total of 67 reservoirs as well as 40 “basins” and other defense measures in Prague parks.
The protective air raid water reservoir on Lesser Town Square was built in the empty space in front of the building of the former Jesuit profession house (today the location of the Mathematical and Physics Faculty at Charles University), the German army also used it during the war. In the background on the northern side of the square, the Renaissance Smířický house no. 6/III (no. 18 or At the Montág's) stands, remodeled in the second half of the 18th century. The parliament of the Czech Republic resides in the palace today. According to Oldřich Máhler the house suffered only minor damage during the uprising.