I have been awaiting the arrival of Byzantium with a strange mix of excitement and trepidation. Excitement, because these are underexplored stretches of art’s global output that are certain to offer surprises. Trepidation, because Byzantium is Byzantium: an empire notorious for its knuckle-rapping religious seriousness and its orthodoxy — a byword for the stern and the hierarchical. If ever a show appeared, by its very presence, to be criticising the way we live and think today, that show was surely going to be Byzantium.

However, I was wrong, for two reasons. First, because I had underestimated the ability of the Royal Academy’s designers to construct a sumptuous journey through this sometimes stern but always glorious religious bling. And second, because Byzantium, on this evidence, was not the cruel and controlling force for orthodoxy we have so long imagined it to be. Variety, naturalism, experiment and perhaps even tolerance were included in its make-up. In its plush, coffee-table-ish way, this stunning display finally succeeds in conjuring up a new Byzantium.

That said, how could we ever have believed in the immobile and monocultural Byzantium of legend? The timescales involved are so huge that no culture in history could have remained unchanged throughout them. The birth of the Byzantine empire is neatly dated to AD330, when the Roman emperor Constantine, having converted to Christianity, founded his new Rome on the site of the old Byzantium, on the banks of the Bosphorus, and called it Constantinople. And the empire’s end can be dated just as neatly to May 29, 1453, when the new Rome was captured by the Ottoman Turks and claimed for Muhammad. Thus, the full story of Byzantium spans more than a millennium of dense Asio-European history. A large chunk of late antiquity, the whole of the Middle Ages and a decent slab of the Renaissance can be fitted into it. Of course there would have been variety.

The trick to encapsulating the output of such a huge stretch of cultural territory successfully depends on subtraction rather than addition. Anyone can put the whole lot in front of you and say: “Make sense of that.” A harder ask is to identify the milestones and the turning points, and to construct a telling journey between them.

The first thing you see here is an inordinately large copper chandelier, in which a baffling number of crosses and candles sway like a rusty Calder mobile across the RA’s central octagon. What drama. The gigantic chandelier — the biggest, I suggest, you will ever see — manages to convey simplicity as well as complexity; heavyweight religious passion and feather-light religious joy. It dates from the 13th century, a long way into the Byzantine story. But the agenda it sets so successfully promises drama and beauty, surprises and size. And that’s what you get.

Having foolishly imagined the art of Byzantium to have arrived at its start line with all its subsequent stiffnesses in place, I found it thoroughly enlightening to watch it finding itself so oddly. The show’s earliest stretch looks at the continuing influence of classical models on the new empire’s art. A Jonah being swallowed by a sea monster, carved out of marble, twists and fidgets like a miniature version of the snake-strangling recorded so momentously in the Laocoön. Marble. Movement. Male nudity. Monsters. None of it is expected. At this stage, it is predictably difficult to differentiate between the last gasps of the Roman empire and the first cries of Byzantium. A Christian mosaic displaying lively personifications of the months — February holds a duck, April a lamb — may have been inspired by “Pavlos, priest and teacher of the divine word”, but it is basically indistinguishable from its late-antique predecessors.

The true spirit of Byzantium begins appearing, instead, in the fabulous horde of carved ivories that now arrive at the show. Their first subjects — a deer hunt, Apollo chasing Daphne — are taken still from the catalogues of Roman paganism, but slowly, beautifully, the carved ivory’s potential for intense Christian messaging is discovered and explored. It may be only elephant bone, but bone is bone, and every Byzantine ivory brings an air of skeletal hush to any subject it illustrates. By the time we reach the 10th century, a fully formed Byzantine aesthetic is giving us a Christ Pantokrator who stares out at us as sternly as a High Court judge delivering a death sentence. Which the ivory seems somehow to guarantee.

Set mostly in twilight, the show does a decent job of implying the solemn religious atmospheres for which most of this art was made. But the melodrama is smartly rationed. And even the notorious Antioch Chalice, the ornate silver cup from the Met in New York that was once thought to be the original Holy Grail, is dealt with sensibly and studiously.

Byzantium’s dangerous location on a busy crossroads between East and West brought a huge variety of influences to its doorstep. Some stretches of the show appear thoroughly Muslim. Others seem to have come straight out of the saddlebags of a passing crusader from Limoges. But this aesthetic good fortune could lead quickly to tragedy. The most notorious event in the empire’s action-packed history was the violent iconoclasm that erupted in the 8th century when the emperor, Leo III, placed a ban on the manufacture of religious images. Leo, I read, was probably mimicking the nearby Muslim example — just as the Muslims had probably inherited their reluctance to worship images from Jewish converts to Islam. Whatever the origins of this terrible urge, the outcome of the image wars was startling.

When the bouts of iconoclasm finally ceased, a century later, Byzantium threw itself into the mass production of religious imagery with the enthusiasm of a released prisoner. The show has enough self-control not to drown us in the resulting flood of interchangeable icons. Their gradual unveiling is impeccably handled. But it is now that the real dangers of orthodoxy begin to show up. Strict instructions were drawn up for the presentation of Christ. Even the lines on his face were counted.

With a sense of theatre that is to be thoroughly commended, the show culminates in a set of stupendous icons from the mysterious monastery of St Catherine on Mount Sinai, where nothing has changed for 1,500 years. You can mistake this firmness of purpose for stasis if you choose. Or you can celebrate it as a rare and precious display of continuity in a world that changes too readily. Over to you.

Byzantium 330-1453, Royal Academy, W1, until March 22

www.waldemar.tv

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010