Constantinople's last extant Byzantine imperial palace, 5 km (3 miles) northwest of Sultanahmet in the Byzantine City Walls (map), is just a shell, but it's being restored, and it gives a fine idea of what the emperor's residence might have looked like in Byzantine times.
Built into the city walls only a short walk from the Kariye Museum (Chora Church), this late Byzantine palace (called in Turkish Tekfur Sarayı, 'Emperor's Palace') dates from the late 12th or early 13th century. It was part of the larger Blachernae Palace complex, used as the imperial residence during the last days of theByzantine Empire.
It was constructed for Constantine Paleologos, son of Michael VIII Paleologos. As heir to the throne, Constantine was know as the Porphyrogenetus ('Born to the Purple,' that is, to wear the color reserved for the emperor).
It suffered damage during the cannonades of the Ottoman conquest of Constantinople (1453), and later served as part of the sultan's menagerie, later as a brothel, then as a pottery workshop and a poorhouse before being abandoned in the later 1700s.
Imagine it filled with Byzantine courtiers, or elephants, or pots, or poor people, or (ahem) prostitutes. At various times it was!
It was closed in 2006, is still closed in 2013, and is now actively under restoration, to be opened later, probably as an exhibition space and conference center.
As you will be right in this area visiting the Kariye Museum, the City Walls and the Mihrimah Sultan Mosque, it's worth taking a look.
On Sunday mornings there's a lively pet bird market at the Altınay Spor Kulübü field on the southwest side of the palace—an interesting affair, particularly for pigeon fanciers.
Other sights to see in this area include the Eyüp Sultan mosque, Pierre Loti café and Ecumenical Patriarchate. You can see them all easily on an Istanbul city tour. More...