English: The Strolling through Istanbul guide has it the Zal Mahmut Paşa mosque is the "grandest and most interesting mosque in Eyüp, a mature but unique work of Sinan." Zal "was a rather unsavoury character, when in 1553 Süleyman had his son Mustafa put to death, it was Mahmut (who got his forename Zal from that of a Persian hero famous for his Herculean strength) who overcame the young prince’s resistance and strangled him. Later he married the Princess Şah Sultan, sister of Selim the Sot, as a reward, it is said for having smoothed that prince’s path to the throne by the elimination of his brother. In 1580 Zal and his wife died in a single night. The külliye has an awkard form because of the available grounds. They slope, so under the mosque there is a vaulted substructure, containing rooms for a lower medrese (there are two medreses). In the lower grounds there is a mausoleum for the founder.