'A Miracle in Wood' the story of St Mary's altar in Krakow

Central panel of Wit Stwosz (Veit Stoss) altar

This year more three million from around the world descended on Kraków for World Youth Day with Pope Francis. Many of them will have visited St Mary's Basilica by the market place in the city centre - Jo Siedlecka tells the story of the medieval altar, and the artist who created it.

It's been described as 'a miracle in wood'. St Mary's Altar, towering behind the high altar of St Mary's Basilica in Kraków, is the largest Gothic altarpiece in the world and a national treasure of Poland. For centuries, pilgrims have come from around the world to gaze on this masterpiece.

The work consists of 200 fine wooden sculptures, painted in vibrant colours and gold leaf. The central part, with huge 2.7 metre tall lifelike statues, depicts dramatically the death of the Virgin Mary, surrounded by the twelve Apostles. Looking upwards, one sees the Ascension of Our Lady and Our Lord, and hovering over that at the top there is the Madonna's Heavenly Coronation by the Trinity, flanked by figures of the Slavonic patrons, Saint Stanislaw and Saint Adalbert of Prague.

The wings of the altarpiece are covered with detailed relief scenes from the life of the Holy Family including a Nativity scene with the Three Wise Men. At the base there is the family tree of Our Lady. While most of altar was carved in limewood (linden) - each of the large figures are hewn from an individual tree - other decorations are made from oak, and the background is constructed in fine larch wood. For the medieval pilgrim, often unable to read, this breathtaking altarpiece would have served as a huge visual catechism.

The altar is the magnum opus of Veit Stoss (in Polish Wit Stwosz) a German artist who dedicated twelve years to the project.

The extraordinary life of Stoss, illustrates how far some people managed to travel in Europe in medieval times, in spite of the hardships of long days on horseback, journeying by horse-drawn carriages carrying equipment and materials, or sometimes even on travelling on foot, on largely unpaved roads - through mountains and forest often inhabited by wolves and bears. The technical brilliance of his work was also accomplished with the simplest of tools.

Born in Horb am Neckar in southwest Germany, before 1450, little is known about his childhood, but as a young man Veit Stoss was apprenticed to the Dutch sculptor Nicholas of Leyden, who worked in Strasbourg, Constance, and Vienna.

In 1468, Stoss achieved the rank of master sculptor. He also traveled in Swabia and the Rhineland to further his artistic education.

In 1473, he moved to Nuremberg, where he married Barbara Hertz and set up a workshop. Here their first son Andreas was born.

No known work survives from that time, but his reputation must have been very good, because four years later, in 1477, Veit Stoss was offered a large commission by the townspeople of Krakow in southern Poland, to carve the biggest Gothic altarpiece ever, for the city's largest church.

Stoss brought his young family to Krakow, set up a new workshop and employed several other sculptors as well as apprentices, to undertake the project. He also assumed the more Polish name of Wit Stwosz.

The inauguration Mass must have been a wonderful event. After completing his masterpiece, Veit Stoss went on to produce many more statues, tombs, bas-reliefs, and engravings in Krakow, including the Crucifix in the east end of the south aisle of St Mary's Basilica, a marble Sarcophagus of King Casimir IV in Wawel Cathedral next to the Royal Castle, a sandstone bas relief Scene in the Garden of Gethsemane - the original is in the National Museum in Krakow, while a copy can be seen in Plac Mariacki Square. His beautiful St Ann with Our Lady and the Baby Jesus is in Krakow's church of St Bernard.

From 1484, Veit Stoss also worked as the municipal architect of Krakow.

In 1486 he left for Nuremberg and Passau to take up further studies for a year. Some historians believe that Stoss drew the blueprint for Krakow's barbican, built in 1499, the largest medieval fortification of this kind in Europe.

Perhaps Veit or his wife felt homesick for Germany, because in 1496, he passed the family business in Krakow on to his son Stanislaw, who was also becoming a successful sculptor, painter, and goldsmith in his own right and moved back to Nuremberg in Germany with his wife and their eight other children - where they lived until his death 37 years later.

Between 1500 and 1503 Stoss executed many outstanding sculptures throughout southern Germany including an altar, now lost, for the parish church of Schwaz, Tyrol of the 'Assumption of Mary'. He also created the altar for Bamberg Cathedral and various other sculptures in Nuremberg, including the Annunciation and Tobias and the Angel. But critics say none of this body of work compares with his beautiful high altar in St Mary's church in Krakow.

For a time Stoss suffered terrible disgrace and was shunned when he was accused of forging a signature on a document and arrested in Nuremberg. He was initially sentenced to death, but later the punishment was commuted to branding on his cheeks with a hot iron. Somehow he survived this crisis. He had some influential supporters and, in spite of being banned from Nuremberg, eventually returned and went on to produce several more notable works in his later years. Among them, during the period 1515-1520, there was a commission for sculptures for Raffaele Torrigiani, a rich Florentine merchant. In 1516 he made Tobias and the Angel, now in the Germanisches Nationalmuseum, Nuremberg, and a statue of Saint Roch for the Basilica of Santissima Annunziata in Florence.

In his final years, Stoss suffered from failing eyesight - the story is movingly depicted in Jan Matejko's 19th century oil painting 'Blind Wit Stwosz with His Granddaughter' which can be seen at the National Museum in Warsaw.

He died, in what must have been his late 80s, on 20 September 1533, and was buried at St Johannis cemetery in Nuremberg. His artistic legacy was continued by his son Stanisław - but his first and greatest work - St Mary's Altarpiece - remains his greatest achievement.

A few weeks before the outbreak of the Second World War and the German invasion of Poland, the Catholic church authorities took the altar apart and stored its main statues in crates, dispersed across the country to save it from being plundered. In 1941, the hiding places of these precious objects were located by a specialist Nazi unit called the Sonderkommando Paulsen. Taken and transported to the Third Reich, on the order of Hans Frank, the governor general of that part of occupied Poland, the crates were placed in deep vaults under Nuremburg Castle.

This formidable ancient building was also being used as a prison for captured Polish soldiers. A group of them discovered the crates containing the altar and sent messages to members of the Polish resistance, informing them that they were there. The altar survived the war in spite of heavy bombardment of Nuremberg by the Allies, and was eventually found by Count Emeryk Hutten-Czapski, who attached to the Polish 1st Armoured Division.

In 1946 it was returned to Poland, where it underwent major restoration, and was finally restored St Mary's Basilica in 1957.

The life story of Veit Stoss has been featured in opera, film and television series - notably in Judith Weir's opera, The Black Spider and the Polish film 'The Story of Yellow Slippers' about his life in Krakow. Images from the altarpiece have been used in several series of Polish postage stamps and often reproduced as prints - but nothing can replicate the experience of seeing the altar in real life.

St Mary's Basilica, also known as the Church of Our Lady Assumed into Heaven is a Brick Gothic church re-built in the 14th century (originally built in the early 13th century), adjacent to the Main Market Square in Kraków.

On every hour, a trumpet signal--called the Hejnał Mariacki--is played from the top of the taller of St Mary's two towers. The plaintive tune breaks off in mid-stream, to commemorate the famous 13th century trumpeter, who was shot in the throat while sounding the alarm before the Mongol attack on the city. The noon-time hejnał is heard across Poland and abroad broadcast live by the Polish national Radio 1 Station.