The church is constructed over the cave that marks the birthplace, with the original basilica commissioned by Constantine and his mother St. Helena, and completed in 339 AD. The church was later destroyed by a Samaritan Revolt in the 6th century AD. In 565 AD a new basilica was built during the Byzantine Empire respecting the previous architectural structure of the original building, including portions of the floor mosaic which survive from this period, and in the center, a 4-meter-wide hole surrounded by a railing provided a view of the cave. The church since has had many additions including a large bell tower.
In the scriptures, the birth of Jesus is narrated by Matthew and Luke, with both accounting that the birth place of Jesus was Bethlehem, and raised in Nazareth. According to Luke 2:7 (traditional translation), Mary "laid him in a manger because there was no room for them in the inn." But in Greek can also be translated to, "she laid him in a manger because they had no space in the room" — we should perhaps imagine Jesus being born in a room in the back of an overflowing one-room house.
The scriptures don't mention Jesus being born in a cave, however less than a century later, both Justin Martyr and the Infancy Gospel of James say Jesus was born in a cave. This is reasonable, because many houses in the area are still built in front of a cave. The cave part would have been used for farm animals and storage - therefore the manger.
Some things to see in the church is the Door of Humility, a small rectangular entrance, created in the Ottoman period to prevent carts to enter, and for dismounting horseman when entering the holy place. The doorway was reduced from an earlier Crusader doorway, the pointed arch of which is still seen today above the current door. The 44 columns with Crusader paintings of saints and the Virgin and Child. You we’ll see fragments of the wall mosaics dating from 1160s. The mosaics feature rich designs with birds, flowers, and vine patterns from Constantine’s church. The baptismal font in the south aisle from the 6th century, the Greek Orthodox main altar on the east end, and the Armenian altar of the Three Kings, commemorating the Magi who tied up their horses nearby, and another Armenian altar in the north apse commemorating the Virgin Mary. Of course during your Christian tour to the Nativity you will also see the Grotto of the Nativity, entered by a flight of steps by the main church altar, this is the cave that has been honored and visited by hundreds of thousands of holy land pilgrims as the site of Christ's birth since at least the 2nd century. Here you will find the silver star on the floor marking the very spot where Jesus was born. In Latin it reads "Here of the Virgin Mary Jesus Christ was born — 1717." See the bronze gates at the north and south entrance to the Grotto added from Justinian’s 6th century building. Only some steps away is the Chapel of the Manger, managed by the Roman Catholic Church, with a leading door to the north apse to the Church of St. Catherine.
Many who travel to the holy land on a guided tour, often say their experience at the Church of Nativity is perhaps on of their most memorable ones. When traveling to the Holy Land, make sure you Israel tour itinerary stops at the Church of Nativity.