A few nice christian travel sites images I found:
Ayasofya
Image by eldan
Ayasofya is much older than the other big buildings of Istanbul, because it was originally the Byzantine Church of holy wisdom. This building survives from the 6th Century (on the site of an even older church). When the Ottomans conquered Istanbul, they rededicated it as a mosque, and painted over the old mosaics because Islam prohibits depictions of people. Shortly after the secular Turkish Republic was founded, the place was turned into a museum, and a restoration effort started, though the restoration has itself been controversial because important Christian art is often covered by important Muslim art, so it’s not always possible to preserve both.
Basilica de San Pedro
Image by Javier Corbo
The Papal Basilica of Saint Peter officially known in Italian as Basilica Papale di San Pietro in Vaticano and commonly known as St. Peter’s Basilica, is a Late Renaissance church located within the Vatican City. St. Peter’s Basilica has the largest interior of any Christian church in the world. It is regarded as one of the holiest Catholic sites. It has been described as "holding a unique position in the Christian world" and as "the greatest of all churches of Christendom".
Basilica de San Pedro
Image by Javier Corbo
The Papal Basilica of Saint Peter officially known in Italian as Basilica Papale di San Pietro in Vaticano and commonly known as St. Peter’s Basilica, is a Late Renaissance church located within the Vatican City. St. Peter’s Basilica has the largest interior of any Christian church in the world. It is regarded as one of the holiest Catholic sites. It has been described as "holding a unique position in the Christian world" and as "the greatest of all churches of Christendom".