The Defterdar Mahmut Efendi mosque (Defterdar = Lord high treasurer) is ancient in foundation (it seems to be by Sinan), but it was wholly rebuilt in the 18th century. Strolling through Istanbul calls it “of little interest in itself” and I agree (though the setting is nice, in a small garden off a very busy road where traffic speeds along if is not stuck. In the garden is the founder’s open türbe, with a dome supported on arches with scalloped soffits, which I show also.