Wozniacki summited the mountain alongside her husband, parents, brother and mother-in-law. (Caroline Wozniacki)

Caroline Wozniacki has never been one to shy away from a challenge—as evidenced by her 2014 mid-career marathon—and even in retirement she continues to live life to the extreme. 

For a Danish Discovery Channel show called "Undressed to the Top with the Wozniacki Family," Wozniacki summited Mount Kilimanjaro alongside her husband, parents, brother and mother-in-law.

"WE DID IT!! Climbed the highest freestanding mountain in the WORLD!!," she wrote in an Instagram post on Wednesday. "Definitely one of the hardest things I have ever done in my life! What a feeling!!"

As is typical for TV, the show was pre-recorded. Currently, firefighters are battling a series of blazes on the mountain. 

Wozniacki, who retired young at just 29, surely has many more adventures ahead of her. 

Check out Wozniacki's episode of the TENNIS.com Podcast: