Singing Ave Maria, holding hands in prayer, falling into each other's arms crying or strolling past shops selling t-shirts with photos of the Argentine pontiff, pilgrims from all over the world have been gathering on and near the sprawling, white Catholic shrine this week.
Among them were Regina and Leonardo Berba, a couple from Manila in the Philippines, celebrating their 30th wedding anniversary with six of their seven children.
"It's our thanksgiving. We feel that Mama Mary has always been there to guide us," said Regina, 54, standing near a giant sculpture of a rosary.
Altogether, up to a million pilgrims are expected to descend on Fatima by foot, car or plane from countries as varied as China, South Korea, Mexico and Venezuela.
'Miracle' boy
The Virgin is said to have appeared six times in Fatima, north of Lisbon, between May and October 1917 to three impoverished, barely-literate children -- Jacinta, 7, Francisco, 9, and their cousin Lucia, 10.
She apparently shared three major prophesies with the trio at a time marked by the ravages of the First World War and Church persecution in a relatively new Portuguese republic.
These reportedly included a warning of a second war and the rise of communist Russia.
On Saturday -- the 100th anniversary of the first reported apparition -- Pope Francis will canonise Jacinta and Francisco, who have officially been found responsible for two miracles.
One of these apparently took place in 2013, when a five-year-old Brazilian boy called Lucas recovered at lightning speed after falling more than six metres (20 feet) down to the ground from a window, smashing his skull.
His parents had prayed to the late Jacinta and Francisco for help.
"The doctors, including non-believers, weren't able to explain this recovery," his father Joao Batista told reporters in Fatima on Thursday.
Closed airspace
Many pilgrims have trekked for days on foot to the central Portuguese town -- some finishing the journey to the small Chapel of the Apparitions on their knees.
Jose Manuel Pinheiro, 42, said he had walked 242 kilometres (150 miles) from northern Portugal in seven days.
"I had promised to come on foot if my wife recovered from an illness diagnosed in 2007," he said, standing next to the chapel.
"She recovered and since then I come every year."
This time round, though, will be hugely different as Pope Francis himself participates.
"With Mary, as a pilgrim of hope and peace I travel to Fatima tomorrow," the Argentine pontiff tweeted Thursday.
He leaves Rome at 2pm local time (1200 GMT) and lands more than two hours later at the Monte Real military base, north of Lisbon.
After a welcome by Portugal's President Marcelo Rebelo de Sousa, he will travel to Fatima by helicopter.
There, he will arrive on the giant esplanade that faces the Sanctuary of Our Lady of Fatima in a "Popemobile" brought specially from Rome -- welcomed by some 400,000 faithful.
Countless others will follow proceedings on giant screens and television sets.
The day's events -- and Saturday's canonisation -- take place under high security.
Some 6,000 members of security and emergency services have been mobilised.
Cars will be banned from the immediate vicinity of the sanctuary, the airspace above will be closed and measures for jamming electronic signals implemented to prevent any flights of drones.
Border controls, meanwhile, have been reinstated in the EU country through the weekend.
burs-mbx/cw/tm
Eyewitness? Submit your stories now via social or:
Email: news@pulselive.co.ke
