Hagia Irene

Hagia Irene (Aya İrini) sits at the quiet end of the First Courtyard of Topkapı Palace, behind the ticket kiosk and the museum entrance. Most visitors walk past it on their way to Topkapı proper without realizing what they skipped. This is the oldest Byzantine church in Istanbul still on its original footprint — Justinian built it in the 530s, just before he built Hagia Sophia, and it served as the cathedral of Constantinople until Hagia Sophia opened in 537.

The Ottoman conquest in 1453 left Hagia Irene as one of the few churches not converted into a mosque. It was used as an arsenal, then a warehouse, and then as the first museum of antiquities in the Ottoman Empire (Müze-i Hümayun, opened 1846). Today it sits empty most of the year, opening only for occasional concerts and the rare special exhibition.

The interior is austere — naked brick walls, the original apse, a single dome. The atmosphere has the ageless-Istanbul feel, half forgotten. Walk around the exterior on the outer wall of Topkapı to see the well-preserved later mosaic courses in the brickwork. A small sign marks it; otherwise it could be a stable.

If you're visiting Topkapı, give it 15 minutes — the layered brick courses outside and the stripped-back interior are a perfect counterpoint to the gilt-drenched palace next door.