Bulgarian St. Stephen Church (Iron Church)

The Bulgarian St. Stephen Church is the only surviving cast-iron church in the world. It was prefabricated in Vienna by the engineer Rumpelmayer in the 1890s, shipped in pieces down the Danube and across the Black Sea, and reassembled on its current site in 1898. The whole structure — walls, columns, even the bell tower — is wrought iron. The interior is decorated in carved and gilded iron in a Neo-Byzantine style, with a central dome, iconostasis, and chandeliers all part of the same metal skeleton.

The church sits on stilts over a small inlet of the Golden Horn, with a footbridge connecting it to the Fener shoreline. The setting, between the Greek Patriarchate uphill and the water below, makes it one of the more atmospheric spots in the city. It's an active Bulgarian Orthodox church, so visitors should dress modestly and be quiet during services.

Most visitors pair this with a walk through the Fener–Balat neighborhood — the colorful pastel houses on the slopes above, the Patriarchate, and a stop at a Çay bahçesi (tea garden) looking over the water.