The Fifth and Sixth Hills - Strolling Through Istanbul: The Classic Guide to the City - page 261

Fat Ali, or sometimes Kalın Ali, Ali the Bear. He was one of the great
characters of his time and was known for his wit and conviviality as
well as for his honesty, a pleasant contrast to his predecessor Rüstem
Paşa. Ali Paşa was a Dalmatian by birth and had been educated in
the Palace School at the Saray, later becoming in turn Ağa of the
Janissaries, Beylerbey of Rumelia, Second Vezir, and finally Grand
Vezir. Since he died in office in 1564, the medrese must have been
built before that time. It is a work of Sinan but presents no special
features except the two symmetrical entrances on either side of the
dershane.
CISTERN OF AETİOS
Continuing along the main avenue for about 100 metres we come
to one of the three huge ancient open cisterns. Its attribution was
for long in doubt, but it has been identified with great probability
as that built by a certain Aetios, a Prefect of the city, in about A.D.
421. Large as it is, it is yet the smallest of the open cisterns in the
city, measuring 224 by 85 metres; it was probably about 15 metres
deep. Like the others, it was already disused in later Byzantine times
and was turned into a kitchen garden. It now serves as a sports arena
known as the Vefa Stadium.
PANAGHİA URANON CHURCH
If so inclined, one may now pursue, part way down the valley that
divides the Fifth from the Sixth Hill, the traces of some very ruined
and insignificant Byzantine churches, scarcely worth the trouble of
finding except for the fun of the search. We descend the flight of
steps at the south-east end of the stadium and continue ahead on
Kelebek Sokağı. At the end of the street we turn left on Kurtağa
Çeşme Caddesi, after which we take the third turning on the right
on to Dolmuş Kuyu Sokağı. Along this street there were formerly
the exigious remains of two Byzantine churches, known locally as
Odalar Camii and Kasım Ağa Mescidi, but these have now virtually
disappeared. They have been identified as belonging to the Byzantine
Monastery of the Theotokos of Petra, but the identification is highly
uncertain.