Time has exposed many of the European explorers who first ventured into Africa as prone to the occasional bout of exaggeration. Yet, oddly enough, in the early Victorian era, when large parts of the African interior remained a cartographic enigma, it was as often as not totally accurate reports that drew ridicule from contemporary geographers.

Think of the German missionary Johan Rebmann, whose description of snow-capped Kilimanjaro in 1846 made him a laughing stock in European exploratory circles. Or poor Speke, who never lived to see the day when his outlandish claim that the White Nile rose from the northern shore of Lake Victoria would be accepted as fact.

Perhaps the Portuguese priest Francisco Alvares was granted a sneak preview of the fate that would later befall Rebmann and Speke when, travelling through the Ethiopian highlands in 1521, he was taken to see the rock-hewn churches of Lalibela. Alvares could scarcely believe what he saw, and his aborted description of the churches concludes simply and ruefully that "it wearied me to write more of these works, because it appears to me they will accuse me of untruth".

The modern visitor to Lalibela might spare a thought for Alvares. Even today, there is something that beggars belief about this vast subterranean complex of rock-hewn churches-justifiably regarded as a contender for the Eighth Wonder of the World. The architecture of the churches alone is astonishing, yet to describe Lalibela as architecturally impressive would be as reductive as calling Victoria Falls an unusually pretty cataract. Lalibela is unique, and if there are words that fully capture the impact of the churches, I have not read them, nor can I find them within me.

Lalibela is set at an elevation of 2,630m among the rugged mountains and amphitheatres that characterise northern Ethiopia. It rose to prominence as the capital of the Zagwe dynasty which reigned over Ethiopia for several centuries prior to AD 1270. In Zagwe times, Lalibela was known as Roha; only much later would the town be renamed in honour of the most revered of the Zagwe rulers, King Lalibela (see Ed 3, page 58).

Tradition holds that the entire church complex at Lalibela was constructed during the reign of the synonymous king, which began in 1167 and lasted for 40 years. One cannot give much credence to these dates, since a reign of precisely 40 years is recorded for seven of the eleven Zagwe kings, and it seems unlikely that a complex so vast could have been completed in so short a time. Nevertheless, the rock-hewn churches of Lalibela were almost certainly in place by the end of the twelfth century, and it is perfectly possible that they are older than tradition suggests - there is no scientific means of dating a building carved out of rock.

The life of King Lalibela is shrouded in legend. The name Lalibela means "the bees recognise his sovereignty" and was apparently given to the future king after he was covered by a swarm of bees - a sign that he would one day rule over Ethiopia. It is anybody's guess what inspired Lalibela to embark on the excavation of the churches. One narrative holds that the young Lalibela was poisoned by the incumbent king and fell asleep for three days. During this time he was transported to heaven and shown a city of rock-hewn churches which he was ordered to replicate when he became king. Another legend claims that he was driven into exile and ended up in Jerusalem, where he received divine instruction to carve a new Jerusalem from the rocks of Roha.

The traditions agree that Lalibela ascended to the throne after his predecessor had a heavenly vision instructing him to abdicate, and he immediately went about assembling the world's finest artisans to carve his New Jerusalem. The churches were built in two main clusters. The eastern cluster, which consists of five churches and two small chapels, boasts an architectural cohesion suggesting it was conceived as a unified whole. The western cluster of four churches is rather less cohesive; it is likely that two of the western churches were initially excavated for secular purposes and were converted to places of worship at a later date.

There are ten churches in all, part of an extended complex of connecting tunnels, small chapels and courtyards that was carved chip by painstaking chip out of solid rock. These churches are regarded as the architectural apex of an Ethiopian chiselling tradition whose antiquity has yet to be established. In all, some 300 rock-hewn churches are scattered around the country; many are said to date to the fourth century AD, when the rulers of Ethiopia converted to the Christian faith. Expert opinion is that some may have served as temples long before the arrival of Christianity.

The most impressive of the individual churches at Lalibela are the subterranean monoliths. There are four such churches, free-standing entities which were carved below the rock surface, so that their roofs lie level with the ground. The process by which these churches were excavated involved cutting a set of deep trenches downwards into the rock, creating a massive rectangular monolith into which the church itself would be carved.

The most easterly of the churches, Biet Medhane Alem, is said to be the largest rock-hewn monolith in the world, standing 11.5m high and covering an area of 800m2. It is supported by 36 rock-hewn pillars on the inside and another 36 on the outside, giving it a classical nobility reminiscent of an ancient Greek Temple. This Grecian influence could be explained by the conjecture that Medhane Alem replicates the design of Ethiopia's first church, which was built at the town of Axum in the fourth century AD and destroyed by the Jewish Queen Yodit roughly 500 years later.

Another striking church is Biet Giorgis, which lies about 500m west of the two main clusters. Carved in the shape of a cross, this monolithic church must measure close to 15m high and, like Medhane Alem, it lies below the ground, in a sunken courtyard enclosed by steep walls. Biet Giorgis is named after Saint George, the patron saint of Ethiopia. The story is that Saint George was deeply offended when he discovered that none of Lalibela's churches had been dedicated to his name, so he visited King Lalibela, who promised to build him the finest church yet. When the church had been completed, the saint was so enthusiastic to see it that he rode his horse right over the wall into the entrance tunnel, leaving deep hoof prints which can still be seen today!

Bald statistics and cryptic legends convey only a small part of Lalibela's impact. Unlike most other ancient buildings in Africa, the churches of Lalibela are not the crumbling monuments of a dead civilisation, but active shrines of worship. The atmosphere, as you wander through the maze of tunnels that connects the churches, is positively medieval, with hermits sitting Bible-in-hand in their cramped cells, white-robed villagers muttering dedications as they slink past, and eucharistic drumbeats and swaying chants emerging from inside the churches.

It is a scene that has been enacted at Lalibela every day for 800 years, if not longer, and the visitor can only feel a mixture of awe and joy at the realisation that it is not merely the churches of Lalibela which have survived into the modern era, but something altogether more spiritual.

Philip Briggs is a regular contributor to Travel Africa. He is the author of eight African guide books.

Lalibela factfile

Each of the 12th century churches in the complex was excavated below ground level and separated from the surrounding stone by courtyards and galleries. The churches are linked through a maze of subterranean passages. Graves, hermit cells and small chapels have been hewn into many of the walls.

Each church is unique in shape and size, is carved with great precision, is decorated with murals and houses valuable manuscripts and crosses. These shrines have been the spiritual centre for the local people for the past 800 years. The churches are in two clusters separated by the Jordan River.

The Unified Eastern Sector

- The 13 metre-high Bet Maryam that was possibly the first church built and is most popular amongst Ethiopians. An elaborately carved interior includes the original Lalibela Cross, the Star of David and stores for church treasures. Parts of the ceiling are decorated.

- Bet Medhane Alem at 11.5m high and covering 800m2 is the largest church hewn from a single block of stone. It is much admired for its classical nobility.

The twin churches of Bet Debre Sina and Bet Golgolta, which have a dank atmosphere and share one entrance, operate independently. King Lalibela is supposedly buried in the latter which is noted for life-size relief carvings of saints. The Selasie Chapel within is most holy and not open to visitors.

- The chapels of Bet Maskel (only 40m2 in area) and Bet Danaghel, a memorial to 50 nuns martyred in the 4th century and the Tomb of Adam, a cell decorated with murals of past kings of Lalibela, complete this sector.

The Western Sector

- Some of the five edifices of the western complex possibly have secular origins.

- The imposing Islamic-looking Bet Gebriel-Rufael, reached by a wooden bridge over a moat-like trench, may have been the residence of King Lalibela.

- Bet Mercurios appears to have served as a jail and, like Bet Abba Libanos, is built round a cave. The latter has apink-tinged facade that underlies the cave overhang. Inside is an altar light that is said to shine perpetually of its own accord. A tunnel to the Bet Lehem chapel, which is thought to have been a monk's cell, connects the church.

- The 12 metre-high Bet Emanuel is aesthetically the finest church in Lalibela-its precisely-worked architecture being greatly admired.

- Separate from the two clusters is the famous cross-shaped 15m high Bet Giorgis (St George). Locals believe that holes in the stone tunnel walls are the hoof prints made by St George's horse when he rode in to inspect the building. It is possible to view the churches from outside free of charge, but most visitors pay for a three- to four-hour guided tour through the complex.