Since these cities are close by and therefore, the sequences might belong to individuals that have been diverged relatively recently. Hence, there have not been much accumulation of mutations. Therefore, the sequences are closely related, resulting in clustering together in the phylogram.
If the individuals had diverged long ago, they should have been migrated to far away places and in the mean time, should have accumulated more mutations than otherwise.
The photograph is not here, but I did research and found the photograph in question. The architectural feature that the photograph of the Hagia Sophia shows is a dome.
