We used to call them the Dark Ages. They're still hard to see.

Their darkness fell when Rome fell in A.D. 476, and it lasted for five hazy centuries, so much romanticized that if you peer into their shadows what you'll mostly see is Prince Valiant and King Arthur and, in the mist, the Norsemen, whose ship prows are snake-necked dragons. The aqueducts are leaking. The cities in Europe are emptying. The birthrate is declining. Trees are pushing apart the paving stones in the roads. There are pagans in the woods.

In "Sacred Arts and City Life: The Glory of Medieval Novgorod" at the Walters Art Museum, you get to watch the Dark Ages ending suddenly in one swampy corner of far northeastern Europe. It's like a curtain lifting to see the new age come.

Novgorod is a city dear to the Russian soul, a place of old onion-dome churches, and revered icons, and much rich Russian history. Alexander Nevsky (who got his nickname, Nevsky, for defeating the Swedes on the Neva River in 1240) was a prince of Novgorod. Ivan the Terrible is still called that in part because of what he did to Novgorod after marching on the city in 1570. To get there from Western Europe, seafarers sailed through the Baltic Sea, and then through the Gulf of Finland as far east as they could go before turning south into the Volkov River. It's a place where the past lasts.

One reason that it lasts there is that it keeps getting buried -- by leaf litter and pollen and thick, black, rain-washed mud. Every 20 or 25 years since at least the 10th century, the townspeople of Novgorod would resurface their city's streets by placing a new layer of rough-cut pine logs on top of the old ones. That's because their city keeps sinking. If you had lost a toy horse-on-wheels there 1,000 years ago, or a ball, or a coin, or a leather boot, it would probably still be there preserved in the claylike blackness of the oxygen-poor mud. Jesters' masks of leather have managed to survive; so have moccasins with thongs, carved doorposts, bracelets, decorative sleigh parts, little musical instruments, knife handles and pins. The best are in the show.

The Dark Ages were dark not because they lacked lighting. They were dark because they lacked writing. Until Eastern Christianity reached that sodden log-built place in 988, almost nobody in Novgorod, not even the prince himself, knew how to write or read.

But they knew how to trade. Amber, dried fish, furs, especially furs. The people of the region had been trading for centuries -- southward down the rivers to the Black Sea and Byzantium, eastward along the Volga to Moscow, and westward by the sea.

Among the finds from Novgorod is a hoard of 59 silver coins that somebody had carefully hidden in a posthole about a 1,000 years ago. Among the coins on view are denarii from Bruges in Flanders and Regensburg in Bavaria, milaresia from Cologne, and English pennies, too, from Norwich and Hastings and York. To trade that far successfully, to send out bills and orders, to kept track of one's wares, it sure helped if you could write things down.

So rare were books in those days that the most efficient way of making townsfolk literate was by giving them a faith, a monotheistic faith, a religion of the book. Four were then on offer: Judaism, Islam and two kinds of Christianity, one Western with its Latin texts, one Byzantine and Greek.

Old Russian chronicles relate that Prince Vladimir accordingly sent out delegations to investigate the options. Islam was rejected because Muslims do not drink. Judaism because the Jews did not possess a country of their own. Western Christianity was deemed unglorious, but when the ambassadors got to Constantinople, they were wowed.

Especially by Hagia Sophia (built 532-537). "We knew not whether we were in Heaven or on earth," the delegates reported. "We know only that God dwells there among men."

Because it seems a sort of treason to overthrow old gods -- Perun of the thunder, Stribog of the sky, and Mokosh' of the fertile earth -- the transition wasn't easy, at least not in Novgorod. But the new imported faith with its fabulous technology was too powerful to quash.

People there turned en masse to writing. In this show we see it happen. They scratched letters into walls. They cut them into iron. But most of what they wrote was written on peels of birch bark. It seems a sort of miracle, but hundreds of their birch bark notes have managed to survive.

Some are exhortations -- "O priests, avoid drunkenness!" Others are apologies -- "My Brother Hesychius! You are angry for no reason." Many more are merely declarations of existence -- "Stephen wrote this" or "Moses the priest's son wrote this" -- as if to scratch your name was by itself a kind of prayer.

The new religion brought with it a new, stunning style. Instead of wearing Perun's amulets to protect themselves from harm, the citizens of Novgorod soon were wearing medals of St. Nicholas and St. George. They were also painting icons, extraordinary icons. Those on view at the Walters are the glory of the show.

Painting an icon wasn't just painting a picture in egg-based colors. It also was an act of ritualized devotion. Specific rules were followed, specific prayers were said. Only the flattest planks were used. Leaving a frame around the edge, the center was then hollowed, and lined with finest linen, cloth that was then covered with many sanded layers of glue and plaster gesso. Once the image was incised, its background was made glorious with gold leaf stuck on with garlic glue. Only after all of this did the brush painting begin.

In medieval Novgorod, icon painting wasn't called icon painting. It was called "icon writing."

In the late 1970s, the Novgorod diggers discovered, again almost miraculously, the 12th-century icon studio of a painter-priest, Alexis Petrovich, nicknamed "Grechin" ("the Greek"). We know that the place was his because of the birch-bark letters addressed to him commissioning his pictures -- "Paint for me two six-winged angels" -- that were dug out of the mud.

Also found were his icon boards (cut but not yet lined), and his little glazed-clay paint pots, and the amphorae that once held his imported oils, and 1,150 bits of amber, some of it still adhering to the small clay pots in which that costly stuff was melted during the preparation of the varnish that finished his icons off.

Russia changes slowly. So does Russia's art. On view, for example, is a 16th-century icon, "Our Lady of the Sign," which precisely reproduces the potent sad-eyed image said to have miraculously protected the city from its enemies 400 years before. Six centuries are covered by the Walters exhibition, but the 290 objects in it don't change much at all.

Nor do the rich old styles of traditional pre-Christian Northern European art completely disappear. Here are medieval knife handles, fur-coat pins and silver bracelets, and a quite astonishing oak column whose carved knot-work decorations and dense Celtic interweavings eerily resemble those applied to Irish artifacts, and Danish ones, and French ones, in the depths of the Dark Ages many centuries before.

Medieval art like this is seldom seen in Washington. The show was organized in collaboration with both the State Russian Museum, St. Petersburg, and the Novgorod Museum Federation. It's a good one. You can see it only in Baltimore. It won't travel.

Sacred Arts and City Life: The Glory of Medieval Novgorod will remain at the Walters Art Museum, Charles and Centre streets, Baltimore, through Feb. 12. The museum, which is closed on Thanksgiving, is open Wednesday through Sunday from 10 a.m. to 5 p.m. Admission is $10 for adults, $8 for seniors, $6 for college students and $2 for anyone 6 to 17.

"St. George and the Dragon" was painted in tempera on wood in the 15th century.A carved wood column from Novgorod dates to the 11th century. Right, the carved, gilded wood statue from the first half of the 16th century depicts St. Euthymius, archbishop of Novgorod.A wooden doll-horse on four wheels dates to the mid-12th century.