An ancient mosaic hidden for centuries has been uncovered in Bethlehem's Church of the Nativity.

An eight-foot tall angel was found by a team working on the restoration of the fourth century church, which was built by the Emperor Constantine and his mother Helena in 339 AD over what is believed to be the place of Jesus' birth.

It is revered by many Christians as a place of spiritual and cultural significance.

The angel is one of seven to decorate the walls of the church, and was found on the north wall between the fourth and fifth windows. According to the National Geographic, other mosaics made from glass, mother-of-pearl and local stones depict Jesus, his disciples, and his mother, Mary.

The restoration – the first of its kind on the church since the 15th century – began in September 2013 and has so far cost around $10 million dollars. The project began following the UN cultural agency UNESCO listing the church as an endangered world heritage site in 2012.

Before the project the roof was in urgent need of repair, and leaks had ruined a significant number of mosaics and paintings. The roof has now been structurally repaired, and treasured art works restored to their former beauty. A mosaic floor is also in the process of being uncovered.

The church is one of the top tourist attractions in the region, but the number of visitors has slowed since tensions rose last October.

Palestinian presidential advisor on Christian affairs, Ziad al-Bandak, told National Geographic that the resotoration project is about preserving Christian heritage.

"In Iraq we are witnessing the destruction of holy places," he said. "We are trying to protect the cradle of Christianity."