What was at the time considered a masterpiece of Ottoman architecture is now merely a footnote to Sinan's subsequent great works. In fact, Sinan was still an apprentice when he was ordered by Süleyman the Magnificent to build a monument to the memory of his beloved first-born son and intended heir, Sehzade (Prince) Mehmet, who died of smallpox in 1543 at the premature age of 21. The plan of the mosque is an important milestone in the evolution of his works, as it is a simple system of four semidomes supported by four pillars that has been both criticized for being harsh and praised as harmonic. The use of four elephantine pillars is repeated in the Blue Mosque. The layout of the complex, consisting of the mosque, a medrese, a refectory, a double guesthouse, a caravansaray, and tombs, follows no special plan, and indeed the primary school and public kitchens have been cut off from the rest of the complex by the main avenue. The prince's tomb is an octagonal masterpiece of arabesques, rare tiles, and stained glass housing a unique sarcophagus of wood lattice inlaid with ivory. The smaller octagonal tomb adjacent to that of the prince is that of Rüstem Pasa. For many years the Sehzade remained the largest building in Istanbul, but even before the mosque was completed, Süleyman had already ordered the construction of another, grander mosque as a monument to his reign.