Hospitals (bimaristans) were important centres for scientific learning. The voyager from al-Andalus, Ibn Jubayr, was amply impressed by the newly built Bimaristan Nur al-Din, which he noted was both a treatment centre and medical school equipped with a comprehensive library; he also describes ‘the ticking water clock’ he saw at the Umayyad Mosque. Abu al-Fadl Muhammad bin ‘Abd al-Karim al-Harithi, known as al-Muhandis, or ‘the Geometer’, was a resident doctor at the hospital as well as being a multi-talented polymath. It was he who designed the geometric woodcarving on the door of the bimaristan and he also repaired the mechanical clock at the Umayyad Mosque.