Much of the architecture has not changed in style for hundreds of years and some old building techniques survive. The urgent need for restoration work is recognized and some has been undertaken. The State together with UNESCO launched a campaign in 1984 to preserve the old city of San'a; a similar campaign was introduced for the town of Shibam in Wadi Hadramawt. The most distinctive buildings [in San'a] are tower houses, of between four and nine storeys, intended for one family. Built of mud-brick or stone or a combination, depending on the region, they typically contain small rooms, thick outer walls and at the top a large reception room (mafraj). The tower houses in the old city in San'a are of natural stone for the ground floor, with fired brick for the upper storeys. Walls are decorated with bands of geometric patterns formed by protruding bricks, which may be whitewashed annually. The bands surround the windows or mark the different storeys. Arched or semicircular fanlights contain coloured glass in geometric or floral patterns.