St Peter's Basilica
It’s the world’s largest Basilica of Christianity, nested into the heart of the Vatican city, with its 186 metres of length (218 if we consider the porch too), a height of 46 metres in the central aisle, a main dome 136 metre high and 42 metres large in diameter.
The huge façade is 114 metres wide and 47 metres high. It has a surface of 22000 square metres and twenty thousand persons can pray in it.
The indigenous St Peter's Basilica, nowadays forgotten, was constructed by will of Emperor Constantine around 320 AD in the area where Saint Peter had been martyrized (together with other Christians) close to the circus of Nero that, in fact, rose in the vicinity. For about thousand years the Basilica grew and got enriched, but it was also theatre of pillage in the barbarian hordes.