The cities underwent significant growth towards the end of the Caliphate during the period of the taifas. Larida and Turtusha became the most important cities in ath-Thagr al-alaa, and had populations numbering some 15,000. Turtusha was a major port and had shipyards that provided vessels for the Caliph's fleet. Balagha had mosques, defensive walls, military enclosures and an impressive palace (later known as Formós Castle). The cities were centres of political power and tax collection, as well as populous places of trade and craft production.