Malta
The cathedral of Order of the Knights Hospitaller of St John.
Trust me. If you go nowhere else in Malta then go here.
From the gravestones on the floor to the gilt ornamentation of the chapels. It is absolutely awesome. On a par with St Marks.
There is a chapel for each country in the order (other than those countries that adopted the Protestant faith).
And then there is The Beheading of Saint John the Baptist (1608) by Caravaggio.
Fantastic.
Search Been there