The al-Sahl al-Nisaburi astrolabe is part of the collection of mediaeval and early modern astrolabes, the largest in the German-speaking world. The scientific instruments were used as both measuring devices and models of the sky and as such symbolised knowledge of cosmos. The al-Sahl al-Nisaburi astrolabe is one of the oldest preserved examples from the Arabic-Islamic world. The delicately wrought pointers of this exquisite device are worked in valuable silver in the form of dancing dervishes.