sergey zagraevsky, a modern art historian, surveyed hundreds of russian icons and miniatures, from the eleventh century onward. he concluded that most icons painted after the mongol invasion of rus display only onion domes. first onion domes displayed on some pictures of twelfth century (two miniatures from dobrylov evangelie). he found only one icon from the late fifteenth century displaying a dome resembling the helmet instead of an onion. his findings led him to dismiss fragments of helmet domes discovered by restorators beneath modern onion domes as post-petrine stylisations intended to reproduce the familiar forms of byzantine cupolas. zagraevsky also indicated that the oldest depictions of the two vladimir cathedrals represent them as having onion domes, prior to their replacement by classicizing helmet domes. he explains the ubiquitous appearance of onion domes in the late thirteenth century by the general emphasis on verticality characteristic of russian architecture from the late twelfth to early fifteenth centuries. at that period, porches, pilasters, vaults and drums were arranged to create a vertical thrust, to make the church seem taller than it was. it seems logical that elongated, or onion, domes were part of the same proto-gothic trend aimed at achieving pyramidal, vertical emphasis.