Q. See question above. Regarding Islam, however, most Poskim follow the opinion of the Rambam (Hilchos Ma’achalos Assuros 11: 7) that it is not considered Avodah Zarah (Shulchan Aruch Y. D. 124: 6, Taz 4 and Shach 12. See also Ben Ish Chai, Parashas Balak) Therefore, they do not expressly forbid entering a mosque. (Avnei Yashfei 1: 153 quotes HoRav Y.S. Elyashiv Zt’l as ruling that it is not prohibited to enter a mosque.)
Other more contemporary Poskim prohibit entering a mosque as well (Tzitz Eliezer 14: 91; 18: 47). See also Meiri, Avodah Zarah 57a, who quotes Chachmei Sefarad as ruling that Islam is Avodah Zarah.
All Poskim agree that unless there is a compelling reason to do so, one should not enter.
See question 1182 in regard to davening in a multi faith room at an airport, we wrote: “Beis Avi (4: 31), Shevet Hakehosi (6: 83), Menuchas Emes (3: 6: n.24) rule not to pray in a multi-faith space, so is it amply quoted in the name of Rabbi J. B. Soloveitchic zt’l. (See also Remoh O.H. 94: 9, on davening in a non-Jewish hotel).
Horav Shlomo Miller’s Shlit’a opinion is similar, he suggests to daven outside of the non-denominational room.
Care should be taken as an array of diverse faith symbols may be exposed at the entrance of the room.”
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.