Final answer:
Vahan likely felt safe reaching Constantinople because it was a stronghold against Ottoman control and Sultan Mehmed II's respect for Hagia Sophia suggested continuity rather than destruction.
Step-by-step explanation:
There isn't a direct quote in the provided excerpts that specifically states what tells Vahan that he is safe once he has reached Constantinople. However, drawing from the historical context and the texts provided, we can infer that Vahan might have felt safe upon reaching Constantinople because it marked a place where the Ottomans had less control especially before its fall in 1453. Constantinople stood firm against various sieges and represented the last stronghold of the Byzantine Empire. Moreover, accounts of Sultan Mehmed II sparing the beauty of Hagia Sophia upon conquering the city suggest a certain level of respect and continuity with the traditions of sacred spaces, possibly indicating a transition but not total destruction, and therefore a sign of potential safety for those like Vahan seeking refuge from Ottoman dominions.