Inside Grace Kelly's Fairytale Wedding to Prince Rainier 64 Years Later: 'It Was an Incredible Affair'

Sixty-four years ago today, Grace Kelly, then 26, wed Monaco’s Prince Rainier in what remains one of the most fairytale weddings of all time.

The glamorous royal affair was held on April 18 to 19, 1956. Over 600 guests attended the nuptials, including Cary Grant, Aristotle Onassis, Ava Gardner, Gloria Swanson and Conrad Hilton.

“It was such an incredible affair, and it’s left such a mark on people,” the couple’s only son and heir, Prince Albert, told PEOPLE. “What it has meant for people has been incredible. For us, it was — and you’ll have to ask my sisters [Princess Caroline and Princess Stephanie] — for us, it was our parents getting married. But what it’s meant for Monaco, for people around the world, and, how their story continues to fascinate people, that’s something unimaginable.”

By Napoleonic Code and Roman Catholic church rules, the couple were required to marry in both a civil ceremony on April 18 and a separate religious ceremony on April 19.

Held in the Palace Throne Room, the civil ceremony lasted only 15 minutes but ended with a 25-minute long recitation of the more than 140 formal titles Grace acquired by marriage. As soon as the ceremony ended, it was repeated for a newsreel camera.

For her civil wedding, Grace wore the first of two gowns created for her by Hollywood wardrobe designer Helen Rose: a two-piece light pink taffeta dress overlaid with champagne colored lace. Both wedding gowns, handmade in MGM’s studio ateliers, were a wedding gift to the star from her studio bosses.

Then on the morning of April 19, Grace came to Monaco’s Saint Nicholas Cathedral as the world watched.

Among the immensity of details: thousands of white lilacs and lilies of the valley; one wedding ring mishap (Rainier was so nervous that Grace helped him place the ring on her finger) and a six-tiered wedding cake that replicated Monaco’s pink palace and scenes depicting Monaco’s history in sugar.

“Mom said it was ‘overwhelming,’ ” recalls Prince Albert. “That ‘excited’ or the word ‘overjoyed’ wasn’t strong enough to express her feelings. My father said so too.”

As for her dress that day, Grace wore one of the most famous wedding gowns of all time. Fit for a princess, it was a creation of 300 yards of antique Belgian lace and 150 yards of silk, taffeta and tulle created by 30 studio seamstresses.

After the celebration, Grace followed Monaco tradition and traveled to St. Dévote, where she offered her wedding bouquet to Monaco’s patron saint. An afternoon buffet featured caviar, salmon, chicken, jellied eggs, cold lobster, chicken and champagne for 600 before the Princess and her Prince left in sunset for a seven-week Mediterranean honeymoon cruise onboard the Deo Juvante II. (They didn’t sail off as planned but instead anchored off shore after only a brief sail!)

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“It was so exhausting,” Albert tells PEOPLE, that privately they both “said that when they left on their honeymoon and got on the boat, they both just kind of passed out from exhaustion and had a good night’s sleep before they got on with enjoying their honeymoon the next day.”

In her later years, Albert recalls of his mother, “She’d recall ‘going down this street on my wedding day’ and seeing the people there. Dad did as well. He was happiest about the fact that things went so well.”