Saint Isaac's Cathedral
In addition to its big diameter, the dome of Saint Sava has significant interior height as well. With 65 m (from the floor to the ceiling) it is the fourth-tallest dome (by interior height) of Orthodox Christianity, surpassed only by the domes of People's Salvation Cathedral in Bucharest (104 m), Cathedral of Christ the Saviour in Moscow (69.5 m) and Saint Isaac's Cathedral in Saint Petersburg (69 m).