The caliph, in order to propitiate the favour of Heaven, resolved to employ this treasure in the building of a mosque which should transcend by its magnificence every other in the world. He collected architects from all the neighbouring countries, laid before them the plan of a vast edifice, unfettered by the difficulties or expense of its execution.
The architects traced out an immense quadrangle, the sides of which faced the four cardinal points of the heavens. At each corner a tower of prodigious height was placed, of admirable proportions; the top of the structure was surrounded with a gallery and crowned with a dome of gilt copper. On each side of the edifice one thousand pillars were raised, supporting arches of an elegant curve and solid construction, and on the arches terraces were laid out with balustrades of gold of exquisite workmanship. In the centre of the edifice an immense pavilion was erected, whose construction was of so light and elegant a nature, that one would have thought it reached from earth to heaven. The vault was inlaid with azure-coloured enamel and studded with golden stars. Marbles of the rarest kinds formed the pavement, and the walls consisted of a mosaic formed of jasper, porphyry, agate, mother-of-pearl, sapphires, rubies, and other precious stones. The pillars and arches were covered with arabesques and verses from the Koran, carved in relief, and painted. No wood was employed in the building of this wonderful edifice, which was therefore fire-proof. Mohammed spent seven years in erecting this celebrated mosque, and expended on it a sum of two millions of dinars.
Although so old, Hassan Abdallah recovered his health and strength, and lived to be a hundred years of age, honoured with the esteem and the friendship of the caliph.
The mosque built by the caliph Mohammed is still to be seen at Cairo, and is the largest and the finest of all the mosques of that great city.
One day, very shortly after the completion of the mosque, the caliph and Hassan Abdallah were absent for three days on a journey. Mohammed communicated to no one but his first vizir his intention; but on his return he assembled his whole court, and informed them that the object of the expedition had been to bury the casket, with the book and the powder, where it was impossible they could ever be discovered. "I have done," added Mohammed, "what I could to consecrate this wonderful treasure, but I would not trust even myself any longer with so dangerous a temptation."