Catherine Zeta-Jones and Michael Douglas got engaged in 1999, before marrying on 18 November, 2000.
Michael popped the question on New Year's Eve at his home in Aspen, Colorado, with one of the most impressive engagement rings we've ever seen, but we had never considered exactly how much it was worth.
SEE: Catherine Zeta-Jones and Michael Douglas' Welsh love nest revealed
WATCH: Catherine Zeta-Jones and Michael Douglas' life together
The vintage 10-carat side-set marquise diamond ring designed by Fred Leighton is estimated to be worth an eye-watering £310,000-£335,000.
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Catherine Zeta-Jones' engagement ring
Kate Earlan-Charnley, Design Director at jewellers Taylor & Hart provided a valuation of the diamond and told HELLO!: "Catherine Zeta-Jones's 10-carat marquise diamond engagement ring is certainly a showstopper. In addition to the impressive 10-carat marquise centre diamond, set east-west, is a hidden halo of diamonds with a diamond pave eternity band."
Catherine Zeta-Jones' engagement ring (on her left hand)
Kate added that the shape of the rock is said to be inspired by the lips of King Louis XV's lover. As if that wasn’t enough, Kate revealed that the whole thing is likely set in platinum.
READ: Catherine Zeta-Jones is identical to her mum in stunning throwback wedding photo
It's no surprise, then, that Catherine has worn the jewel with pride ever since.
The couple spared no expense for their wedding day, either, held at the Plaza Hotel in New York City. Catherine wore a stunning beaded Christian Lacroix gown, believed to have cost £110,000 ($150,000), and accessorised with a regal tiara.
Reports say that the celebrations racked up a total cost of £1.07million ($1.5million).
Their star-studded guestlist included the likes of Sharon Stone, Jack Nicholson and Brad Pitt.
Catherine and Michael met in 1996, while promoting movies at a film festival in France. Despite a 25-year age difference, their romance continued, and they are now parents to two children: Dylan and Carys.
They celebrated their 20th anniversary together last year, when Catherine shared a special montage of their time together.
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