Bulgarian archaeologists have discovered a rare gold reliquary cross during excavations at a medieval stronghold dating back to the Second Bulgarian Empire.

The 12th century cross was found in a recently unearthed church at Trapezitsa Hill, one of the two main citadels of Veliko Tarnovo. Then called Tarnovgrad, Veliko Tarnovo was the capital of the Second Bulgarian Empire (1185-1396), one of the biggest countries in Europe.

'The finding is extremely rare; it is of utmost importance,' said Konstantin Totev, who leads the team of archaeologists in Veliko Tarnovo, some 220 kilometres east of Sofia, Bulgaria's modern capital.

'It is a gold cross, an encolpion – a work made to hold relics,' he said. 'It is unique because the vast majority of such crosses have been made by bronze and silver.'

The cross was dug up near an altar pillar at the 23rd Orthodox Church at Trapezitsa, he said. The church was near the imperial palace, which covered almost 3,000 square metres, about three-quarters of an acre.

The well-preserved relic, 11 cm in length and weighing 75 grams, which was made in Byzantium, depicts Christ on the cross, his mother, Mary, and a few saints. It is decorated with niello and several palmettes.

Encolpion crosses, crafted in studios in Byzantium, were also known as 'Russian enclopion crosses' because they were copied and distributed widely in Russia from the 12th to the 14th century.

After their conversion to Christianity, the Vikings also imported many of them to Scandinavia.