Such marvels were undreamt of when Pieter Bruegel the Elder painted the first of many representations of the Tower of Babel in 1563, a picture that spawned a host of imitations; they were still decades away when John Martin drew his apocalyptic panorama The Fall of Babylon and only just coming to light when Degas painted his little-known Semiramis building Babylon. They were unknown, too, to William Blake, who in 1795 produced perhaps the most striking Babylonian image of all - showing the naked Nebuchadnezzar, haunted and mad as described in the Book of Daniel, crawling on all fours like an animal. The king, hair in a mane, is drawn in relief, coloured in blues and yellows, just like (although Blake could not know it) the lions that decorated the real king's palace walls. In this extraordinary leap of the imagination, Blake magically linked the physical city with the myth it had become.

Across London, the remains of another legendary civilisation are on display. Byzantium 330-1453 at the Royal Academy comprises some 300 pieces and is the first major exhibition of Byzantine art here for 50 years. From its foundation by Constantine in 330 to its fall to the forces of Mehmet II in 1453 Constantinople saw itself as not just the heir of Christian Rome but a perfected version of it; art was an important part of this self-image. Nevertheless, the show describes a fractured artistic history: for all its longevity, the iconoclastic furore of 730-843 meant that the majority of its early sacred images were destroyed, while the sack of the city in 1204 at the hands of the Fourth Crusade meant that vast amounts of its wealth and artworks were dispersed, much of it to Venice. The dispersal did nevertheless protect numerous treasures from the hands of the Ottoman conquerors.

The exhibits gathered at the RA from the US, Russia, Egypt and Europe are of the highest quality. This dazzling array of icons, metalwork, wall paintings, manuscripts, ivories and perhaps most unexpectedly, textiles, goes some way to showing why the city by the Golden Horn and its empire were viewed with such awe and such covetous, destructive envy by both East and West.