Three capitals stacked on one peninsula: Roman Byzantium, Christian Constantinople, Ottoman Istanbul. This route steps past the headline sights and goes for the reservoirs, obelisks, exiled churches and founding monuments where the layers actually show.
Justinian's 532 AD underground reservoir: 336 columns hauled from older Roman temples hold up a chamber the size of a cathedral, including two Medusa heads set sideways and upside down as recycled rubble. Open 09:00–22:00.
The Byzantine chariot arena where the Nika riots of 532 left some 30,000 dead. Three spine monuments survive: Thutmose III's Egyptian obelisk re-raised in 390 AD, the bronze Serpent Column looted from Delphi, and the stripped Walled Obelisk.
Three buildings holding the Alexander Sarcophagus from Sidon, a cuneiform copy of the 1258 BC Treaty of Kadesh — the oldest surviving peace treaty on earth — and the Tiled Kiosk of 1472, Mehmed II's oldest standing civil building.
Justinian and Theodora's church of Saints Sergius and Bacchus, finished around 536 — a decade before its far larger namesake and widely read as its structural rehearsal. The Greek dedication frieze naming Theodora still runs round the gallery.
Sultan Abdülmecid's 1856 declaration that the empire was European: 285 rooms, 14 tonnes of gold leaf, and a 4.5-tonne Bohemian crystal chandelier. Every clock in the building reads 09:05, the minute Atatürk died here on 10 November 1938.
Pietro Canonica's 1928 monument sculpts the same men twice: Atatürk in wartime uniform on the north face, in frock coat as founding statesman on the south, with İnönü and Çakmak ranked behind him. The republic's founding myth cast in bronze.
Set in Atatürk's own war college, it keeps a length of the great chain that sealed the Golden Horn against Mehmed II in 1453 alongside sultans' campaign tents. The Mehter band, founded in the 1300s, performs most afternoons.
Built in 1892 to lodge Orient Express passengers, with the city's first electric lift. Room 411 is preserved as Agatha Christie's; room 101 is a museum to Atatürk, who stayed twelve times. The Kubbeli Salon still pours afternoon tea.
The finest Byzantine mosaic cycle anywhere, laid 1315–21 for Theodore Metochites, who kneels in the narthex offering the church to Christ. In the side chapel the Anastasis fresco shows Christ hauling Adam and Eve bodily from their tombs.
Seat of the Orthodox church since 1600, spiritual head to some 300 million faithful. Inside sit a patriarchal throne claimed as fourth-century, a column of the flagellation, and relics of Gregory the Theologian returned from Rome in 2004.
The iron church: cast in Vienna in 1898, floated in pieces down the Danube and bolted together on the Golden Horn shore for a Bulgarian Exarchate that had broken with the Patriarchate 26 years earlier. Restored in 2018.
Raised in 1458 over the grave of Muhammad's standard-bearer, killed besieging Constantinople in 674. Here each new sultan was girded with the sword of Osman at accession, and the cemetery of the devout climbs the hill behind it.