Twenty-nine-year-old Iswarin Ashana made a special point to go to the Great Mosque of Malang, East Java, for Eid prayers on Wednesday.

“There is actually a mosque near my in-laws’ house, but I wanted to experience the atmosphere of praying together in the yard of the church that went viral on social media,” she said. “I left early in the morning with seven family members.”

The Great Mosque of Malang started construction in 1890 and was completed in 1903, near both the Immanuel Church, which was built in 1861, and the Catholic Church of the Sacred Heart (Gereja Hati Kudus Yesus), which was built in 1905.

Every Idul Fitri, the mosque hosts tens of thousands of worshippers for Eid prayers, which overflows to the nearby alun-alun (town square), as well as the yards of both churches.

“If the Muslim...