The barriers separate communities which are predominantly republican and nationalist Catholic from those which are predominantly loyalist and unionist Protestant. The earliest barriers began to be constructed after severe sectarian rioting in 1969, at the beginning of the period known as The Troubles. In 1980, there was a major burst of construction. Further barriers were built even after the Good Friday Agreement in 1998 which called a halt to the fighting. The walls were built in several areas in Northern Ireland, rural as well as urban areas, but mostly in Belfast; some have gates which are opened during the day and many bear murals. There are plans to remove the walls gradually but although some have gone many are claimed as still vital to the relative peace which now exists.