From the web I gathered "The tomb of Sheikh Osman Rumi was built as [one of] the most beautiful examples of Seljuk architecture. Although the date when the tomb was originally built is not known, it was decided that a significant part of it was built in the 15th century. Seyh Osman Rumî is one of the 23 saints whose names are listed in the 1868 Konya Yearbook." His brother Hasan is in an neighbouring mausoleum.