other side of the city lie the remains of the ancient Scupi, with ruins of a theatre, thermae and a basilica. The Skopje Aqueduct, between Scupi and the city centre, is rather mysterious because its date of construction is unknown. It seems to have been built by the Byzantines or the Turks, but it was already out of use in the 16th century. It consists of 50 arches, worked in cloisonné masonry. Skopje Fortress was rebuilt several times before it was destroyed by the 1963 earthquake. Since then, it has been restored to its medieval appearance. It is the only medieval monument in Skopje, but several churches around the city illustrate the Vardar architectural school which flourished around 1300. Among these churches are the ones around Matka Canyon (St Nicholas, St Andrew and Matka churches). The church of St. Panteleimon in Gorno Nerezi dates from the 12th century. Its expressive frescoes anticipate the Italian primitives. Examples of Ottoman Turkish architecture are in the Old Bazaar. Mosques in Skopje are usually simple in design, with a square base and a single dome and minaret. There entrance is usually emphasized by a portico, as on Mustafa Pasha Mosque, dating from the 15th century. Some mosques show some originality in their appearance: Sultan Murad and Yahya Pasha mosques have lost their dome and have a pyramidal roof, while Isa Bey mosque has a rectangular base, two domes and two side wings. The Aladža Mosque was originally covered with blue faience, but it disappeared in the 1689 Great Fire. However, some tiles are still visible on the adjoining türbe. Other Turkish public monuments include the 16th-century clock tower, a bedesten, three caravanserais, two Turkish baths and the Stone Bridge, first mentioned in 1469. The oldest churches in the city centre, the Ascension and St Dimitri churches, were built in the 18th century, after the 1689 Great Fire. They were both renovated in the 19th century. The Church of the Ascension is particularly small it is half-buried in order not to overlook neighbouring mosques. In the 19th century, several new churches were built, including the Church of the Nativity of the Virgin Mary, which is a large three-nave building designed by Andrey Damyanov. After 1912, when Skopje was annexed by Serbia, the city was drastically westernized. Wealthy Serbs built mansions and town houses such as the 1926 Ristiḱ Palace. Architecture of that time is very