Along with posting a photo of the two smiling on top of a mountain in Aspen, Colorado, Zeta-Jones said as a caption: "16 years ago, this was the spot where my husband proposed."
Douglas, 71, also posted photos of what he called the "scene of the crime" when he dropped down to one knee on New Year’s Eve in 1999.
The couple has been sharing tons of photos from their snowy spring break trip on their social media accounts. Zeta-Jones, 46, captioned one photo, "Gotta love skiing in the sun!"
The Hollywood couple has been going strong since their brief split in 2013, reuniting the following year.
In an interview with ABC News last July, Douglas said "Catherine and I are great. We're celebrating our 15th anniversary … and my kids are all great."
Douglas and Zeta-Jones, who wed in 2000, have two children together, 15-year-old Dylan and 12-year-old Carys.