Early masonry is basically held together by mass! Exterior walls are typically over 2' (60cm) or more thick and quite often include large rocks.
Historical Orthodox Church in Kiev, the "Domes" are finished in gold leaf.
On these grounds the remains of monks are interned in the tunnels below the church.... I got as far as the base of the steps into the tombs and had to turn around... too claustrophobic for me!