The Tibetan mahasiddha Thangtong Gyalpo was a highly realized Master of the Nyingma- tradition , renowned engineer and bridge builder. He is reputed to have enjoyed a long life and although his exact dates are uncertain, three sets are generally attributed to him: 1385- 1510, 1361-1485 and 1385-1481.Thangtong Gyalpo is said to have discovered important hidden manuscripts during his meditation at Taktshang monastery.

Drubthob Thangthong Gyalpo who is popularly known as Chagzampa, or 'the builder of Iron Bridge', the "King of the Wide Spaces(of consciousness)", as residents called him. He was a famous sculptor, painter, architect, military commander, founder of the Tibetan Opera and also a man who founded schools of Mahayana Buddhism.

As Thangthong Gyalpo is 69 years of life, tirelessly and equipped with an inexplicable energy, he had been on journeys to "the End of the Tibetan World", between Kashmir in the West and Assam in North-west India. On the way he had preached, given initiations, composed songs, healed and meditated, explored new image-worlds, had drawn and painted, helped the travelling bards and had already developed the idea of a Tibetan theater in his head, had done forging himself, which he had learnt as a child, had carved sculptures and discovered that also semi-precious stone like rock-crystal are also suited for culptures. And he had discovered, perhaps, as the legend has it, how to forge stainless iron, especially in the seams, the overlappings, that would last for "Eternity" .

He is best known for the number of iron bridges (chagzam) he built in the country. He is said to have built more than 50-iron bridges and 70 wooden bridges throughout the country. People still wonder how he made the bridges from chains of iron without any visible welding on them. The iron bridges around the region were built in and around 15th century.

His first expedition on the search for iron was motivated by an incident at the ferry over the Kyichu by Lhasa . Thangtong Gyalpo wanted to cross the river, but was scorned by the ferryman because of his eccentric appearance( being dressed as a beggar) and after a blow on his head with the rudder was thrown overboard. This endowed him with an insight into the predicament of the poor and the injustices against them, and he wowed to build a bridge at this very place, so that all people without discrimination could cross the river. This experience served as a catalyst and he consequently embarked on a campaign to build bridges and ferry crossings. His first endeavor was in 1430 at the Chusul River where, with the assistance of two blacksmiths, he forged iron - said to be 'the thickness of an eightyear-old boy's arm'- into chain links, with which he attempted to span the river. The project was beset with problems, and more funding was required. Drawing upon the traditions of the itinerant religious storytellers of his time, Thangtong Gyalpo formed the first operatic troupe in Tibet. The troupe performed and raised the necessary funds to complete the project. Thangtong Gyalpo and his troupe of seven beautiful sisters then toured Tibet, raising money to construct a reputed fifty-eight iron chain bridges and a hundred and eight ferrycrossing stations.

Between 1449 and 1456, he built the Riwoche stupa in a breathtaking setting on the banks of the Tsangpo river, about 400 kilometres west of Lhasa towards the Nepalese border.