The best view of the sixth-century church of Sts Sergius and Bacchus, now the Küçük Ayasofya Mosque, is from the middle of Küçük Ayasofya Caddesi, traffic permitting. Built by Justinian before Ayasofya, it remains just out of reach of the tour buses, although an arts-and-crafts community is growing in its shadow. Sadly, little of its architectural inventiveness is to be seen from the exterior, save for its wobbly dome, but the interior is an artful essay in geometry, contrasting flat and curvilinear surfaces, architraves and arches. Even its curious melon-shaped capitals become part of the geometry lesson. A recent restoration, whilst stripping back some of the building’s charm, makes the byzantine inscription that runs around the dome easier to read.