One word substitute is Belfry.Minaret: a slender tower, typically part of a mosque, with a balcony from which a muezzin calls Muslims to prayer.Chapel: a small building or room used for Christian worship in a school, prison, hospital, or large private house.Belfry: the part of a bell tower or steeple in which bells are housed.Spire: a tapering conical or pyramidal structure on the top of a building, typically a church tower.