According to Wikitravel:
The Basilica of the Annunciation is built above the sunken grotto which according to the Roman Catholic faith was the home of the Virgin Mary and the place where she received the Annunciation (the announcement of the imminent birth of Jesus). The large and impressive modern-day church is built above the remains of churches dating back to Crusader and Byzantine times, still visible on the lower level. The church boasts dozens of pictures donated by Christian communities around the world. The Largest Church in the Middle East and one of Christianity’s Holiest shrines, its imposing dome dominates the Nazareth skyline and is an ideal landmark and starting point for visiting Other churches. It marks the spot where the Archangel Gabriel Informed the Virgin Mary that God had chosen her to bear his son; there is also a tradition that Mary lived in a house on this site. The complex of the modern Basilica is built on two levels. The lower one,Making the traditional Roman Catholic site of the Annunciation, contains ancient remains of churches from the Byzantiane and Crusader eras. During archaeological excavations, relics were found dating back to the Canaanite settlement of Nazareth, Though the most interesting find was of a typical Nazarene house, hewn out of the rock, from the Roman Period. The upper level, built between 1959 and 1969 on the site of an 18th-century church, is in strikingly modern architectural style. With its stained- glass windows highlighted against bare stone.A garden and courtyard connect the Basilica to St. Joseph’s Church and Workshop. Admission to the Basilica is free.
“It marks the spot where the Archangel Gabriel Informed the Virgin Mary that God had chosen her to bear his son” reminds me of one of the most famous episodes in the life of Muhammad, where the Angel Gabriel transported him to Jerusalem before escorting the prophet to heaven. This event is celebrated by the Dome of the Rock.
