One of the two surviving flying buttresses at the Cistercian ruin – which supports a magnificent "three-tiered" 13th century church – has been repaired after becoming distorted.
Conservationists have dismantled 22 of the 26 stones in the buttress and reassembled them using hidden, re-enforcing steel dowels.
John Ward, English Heritage Technical Manager, said he hopes the work will keep the structure secure for many years to come.
He said: "The buttresses are such delicate features, it's a wonder they have survived for so long. Engineers detected that one of them was showing signs of strain after a visual inspection and by examining 3D scans.
"It is most likely that the problem has been caused by ground movement. Dismantling was the only viable option and we have been working on the project for many months to ensure its success."
Stones were carefully recorded during dismantling and precise measurements taken of joint depths and the thickness of masonry. Badly eroded masonry was replaced by newly quarried sandstone and holes were then drilled through the stones and bronze and stainless steel dowels inserted. The conservationists then used a hydraulic mortar lime, similar to the original medieval mix, to fill gaps.
John Lax, visitor operations manager, said the church is often regarded as the crowning glory of English Cistercian architecture.
He said: "According to some experts, it was built to house the shrine of St Aelred, who oversaw Rievaulx's development into one of the great monastic houses of Europe.
"It became the spiritual fountainhead for the spread of the Cistercian creed throughout northern Britain. The abbey we see today is a precious legacy of those times, which requires all our skills to keep intact."