Dalrymple's third book From the Holy Mountain: A Journey in the Shadow of Byzantium (1997) saw him trace the ties of Eastern Orthodox congregations scattered in the Middle East to their ancient origins; it also deals with the question of how they have fared over centuries of Islamic rule and the complex relationship of Islam, Judaism, and Christianity in the Middle East.
In his first book In Xanadu Dalrymple had followed the route taken by Marco Polo from Jerusalem to Mongolia. In this book he follows the route taken by sixth-century monk John Moschos who traveled through the Eastern Byzantium world, culminating at Constantinople, where Moschos wrote his book Pratum Spirituale or The Spiritual Meadow.
Dalrymple's journey in the footsteps of Moschos starts from Mount Athos, Greece, proceeds to Istanbul, and thence to Eastern Turkey. Here he crosses the border and enters Syria. The next stop is Lebanon which is just at the end of its civil war, after which he crosses into Israel, the West Bank and concludes his trip in Egypt at the monastery of Deir ul-Muharraq which had just been attacked by the Gemaat al-Islamiyya.