One of Prague´s attributes is a "hundred-spired". A father of this name was a mathematician, physicist and religious thinker Bernard Bolzano who at the beginning of the 19th century counted 103 towers in Prague. The oldest surviving tower on the territory of Prague is the Black Tower which is a part of Prague Castle fortification and comes from a first half of the 12th century. Approximately at the same time two tovers in a frontage of the Basilica of St.George obtained today´s appearance.