Minaret

Minarets are tall, usually free-standing, structures associated with mosques and used for the call to prayer.

"As well as providing a visual cue to a Muslim community, the main function of the minaret is to provide a vantage point from which the call to prayer is made. The call to prayer is issued five times each day: dawn, noon, mid-afternoon, sunset, and night. In most modern mosques, the adhan is called from the musallah, or prayer hall, via microphone to a speaker system on the minaret." - Wikipedia