There is often a tall tower outside a mosque.  This is called the minaret.  Muslims pray to Allah five times a day.  In the past, a man called a 'muezzin' would climb up the minaret.  He would call out in a loud voice, to tell Muslims that it was time to pray. Nowadays, a tape recording of the call to prayer and loud speakers are often put in the minaret instead.

In the Cardiff mosque, the Call to Prayer is usually recited inside the mosque so as not to disturb the people who live in the area. The majority of these people are not Muslims. But every Friday afternoon, you can hear the Call to Prayer coming from the loudspeakers in the minaret. It calls Muslims to the main service of the week.