After Muhammad's arrival in Medina, the first thing to be done was to build a cathedral mosque. It was constructed on the plot of two orphans, Sohal and Sohail, whom Abu Ayub Ansari paid the price. The ground of the plot was levelled and a mosque, 54 yards width and 60 yards in length was built over it with unbaked bricks and mud, and was roofed with palm-wood rafters. This mosque became known as the "Prophet's Mosque" (Masjid-i-Nabwi) was free from all kinds of artificialites and was a monument of simplicity. Its walls were made of mud bricks, the roof supported by trunks of palm-trees and covered over with the leaves and twigs. The floor was strewn with gravel. In the corner of the courtyard, a sort of a platform with a shed was raised to accomodate those having no home or family. Those who lived there were known as the residents of the Suffa or Platform. This was, so to speak, a kind of seminary attached to the mosque, for these people devoted their whole time to the study of religion. Adjoining the mosque were erected two apartments for the household of Muhammad.