The Stone Gate is part of the remains of the city walls. Although they were first mentioned in 1429, it is assumed to have been built in 1266. Throughout the city's long history it has undergone many reconstructions and were devastated by fires more than once. Last such fire destroyed much of Gradec on 31 May 1731, burning down houses that were close to the Stone Gate. The Gate displayed a painting of the Mother of God, which was miraculously undamaged by the fire. To commemorate the event, grateful citizens built a chapel within the arch of the old Stone Gate. The chapel, which houses the painting of the Mother of God, has become Zagreb's biggest shrine and is regularly visited by people who come to light a candle and thank the Lady for protecting them.On 31 May 1991, the 260th anniversary of the shrine, Mother of God of the Stone Gate was declared as the patron saint of Zagreb, and the date is now officially celebrated as the Day of the City.