I have started reading an abridged translation of the Rihlah--the Travels--of Muhammad Ibn Ibrahim Ibn Battutah, whose wanderings from his native Morocco, between 1325 and 1354, took him as far east as China, and as far south as Timbuktu. Living roughly a generation after Marco Polo, he exceeded the journeys of the better-known Venetian, and arguably anyone else we know of for centuries.
It was a time of relative peace between the Christian and Islamic worlds (the key word here being "relative"). In 1291 the last Christian stronghold in Syria, the fortress of Acre, fell to the Mameluke sultan al-Ashraf Khalil. The Reconquista in Spain was mostly accomplished, save for the Muslim kingdom of Grenada. The fall of Constantinople to the Ottoman Turks was still a century in the future. Trade continued, as it always does, whenever it can, and pockets of minorities got on as well as they could within the larger civilizations.
I have only gotten so far as Ibn Battutah's first pilgrimage to Mecca, by way of Syria. Along the way he visits well-known shrines and tombs and consults with holy men, much as Christian pilgrims did. He occasionally comes across heterodox groups, such as the "revilers" of Sarmin, and is careful to relate their extraordinary doctrines--here, an extreme hatred of the Ten Companions of the Prophet, to the extent that they cannot bear ever the number, "ten." But their presence in an orthodox Sunni world is taken pretty much for granted.
He relates the following from his first visit to Syria:
"I witnessed at the time of the Great Plague at Damascus in the latter part of the month of Second Rabi of the year 749 [July 1348] a remarkable instance of the veneration of the people of Damascus for this mosque [the Mosque of the Footprints]....[A]fter performing the dawn prayer on the Friday morning they all went out together, walking barefoot and carrying Qur'ans in their hands. The entire population of the city joined in the exodus, male and female, small and large; the Jews went out with their book of the Law and the Christians with their Gospel, their women and children with them; and the whole concourse of them in tears and humble supplications, imploring the favor of God through his Books and his Prophets."
There appears, to me, a great humanity in this joint response to a common calamity. It is not, of course, what we would call religious freedom. But it is an unusual marshaling of everyone to common prayer, of the sort that would be unusual even today, either in the secular West or in the Islamic states of the Near East.
And it calls to mind an earlier incident, a Phoenician ship foundering in a great storm,
וַיִּירְאוּ הַמַּלָּחִים, וַיִּזְעֲקוּ אִישׁ אֶל-אֱלֹהָיו, ...; וְיוֹנָה, יָרַד אֶל-יַרְכְּתֵי הַסְּפִינָה, וַיִּשְׁכַּב, וַיֵּרָדַם. ו וַיִּקְרַב אֵלָיו רַב הַחֹבֵל, וַיֹּאמֶר לוֹ מַה-לְּךָ נִרְדָּם; קוּם, קְרָא אֶל-אֱלֹהֶיךָ--אוּלַי יִתְעַשֵּׁת הָאֱלֹהִים לָנוּ, וְלֹא נֹאבֵד.
In great fear the sailors cry, each to his own god....Jonah, though, slinks down into the hold, to be interrupted by the captain: Why are you sleeping? Get up! Call upon your god! Perhaps he will act for us, and we will not be destroyed.
We all know the story--at least the whale part--but of course it ends in Ninevah, where the purported tomb of the reluctant prophet has only lately been destroyed.
I am always dismayed when I hear the ISIS militants called "medieval." Of course medieval people could commit atrocities and acts of cruelty. But we moderns have often given them a run for their money on that score. The demolished tomb, before its destruction, was a simple but strikingly beautiful building, where both Christians and Moslems made pilgrimage for centuries. It was medieval people who designed and built it, the work, roughly, of contemporaries of Ibn Battutah. The iconoclasts who blew it to rubble, disdaining tradition and all reverence for a common (if very human) prophet, were, distressingly, thoroughly modern.