From the Wikipedia: "Pammakaristos Church, also known as the Church of Theotokos Pammakaristos (Greek: Θεοτόκος ἡ Παμμακάριστος, "All-Blessed Mother of God"), later known as Fethiye Mosque (Turkish: Fethiye Camii) and today partly a museum, is one of the most famous Byzantine churches in Istanbul, Turkey. The parekklesion, besides being one of the most important examples of Constantinople's Palaiologan architecture, has the largest amount of Byzantine mosaics after the Hagia Sophia and Chora Church in Istanbul."

Part of the same complex is still in use as the Fethiye Mosque.

I came across a site with reconstructions of Istanbul monuments around 1200, for instance the Monastery of Pammakaristos.