According to Catholicism or Eastern Orthodoxy are there any doctrinal barriers to Christians sharing places of worship with non-Christians?

**Hagia Sophia** was originally the seat of the Patriarch of Constantinople, then the chief mosque of the Ottoman Empire, then a museum. A few days ago, it reverted to being a mosque once more. Numerous Christian religious leaders have decried this last transition (as, in my opinion, they ought to), but it left me wondering what a long-term resolution of the matter would actually look like. The building could, in principle, revert to being a church. Personally, I feel that, given the centuries of history that Muslims have with said structure, this would be unjust; and, in any case, short of a Christian reconquest of Constantinople/Istanbul, it's never going to happen. Atatürk's compromise of turning the building into a museum seems well-intentioned but ultimately unsatisfactory: this building was built for the glory of God. The one remaining option that I can see is to **share the building**. Christianity's and Islam's holy days seldom overlap. **Could the building be a church on Sundays and a mosque on Fridays?** I'm a practising Roman Catholic myself, and I can't think of any *insurmountable* reason forbidding sharing a place of worship outright. There are, after all, stories of Catholic priests celebrating the eucharist in Auschwitz ; I can't imagine that any putative unholiness brought on by reciting the Quran could compete with an extermination camp. But I'm far from an expert, and I hardly need to add that the Eastern Orthodox perspective would be essential in the case of Hagia Sophia. And, of course, **Hagia Sophia is just a prominent example**. There are plenty of other locations, e.g. the Mosque–Cathedral of Córdoba, where it might be reasonable for Christians to share a place of worship with another faith.