TANZANIA, Africa -- Two-time Grand Slam winner Garbiñe Muguruza traded the sun-drenched beaches of the typical tennis off-season for icy mountains this week as she took on one of the biggest challenges of her career. 

Braving sheer cliff drops and sub-zero temperatures, Muguruza scaled the highest peak in Africa during a five-day climb to the top of Mount Kilimanjaro.

Read more: Muguruza ponders Asian Swing reset after US Open exit: 'We need to evaluate things'

“We crossed waterfalls, rivers, icy rivers, caves, cliffs, and the hardest: frozen nights,” Muguruza wrote in social media posts chronicling her journey.

“At some point, I was crying when my guide told me to not look down at the 300 m free fall.”

According to Muguruza’s team, the Spaniard had been planning the climb since this summer, after stumbling upon information on Mount Kilimanjaro while researching African beaches. After consulting with sponsor Adidas on the right gear to use, and chatting with other people who have previously summited Kilimanjaro, she decided to make the expedition.

Accompanied by a friend and a group of guides, Muguruza spent four long days hiking in tough conditions, battling the altitudes and sleeping in tents and sleeping bags as the temperatures dropped below zero. 

Photo gallery: Ranking Rockets: The 20 biggest movers in the 2019 Year-End Rankings over the previous year - plus three honorable mentions

On the fifth day, Muguruza and the party woke up “very, very early” in order to reach the summit at Uhuru Peak, which sits at an altitude of 19,341 feet (5,895 meters). 

But with temperatures dropping down to -12º C, there was no time to stop for rest or sleep. They hiked for 16 hours straight back down to Camp 1 - for a total of 22 brutal hours of hiking on that final day.

“We felt ALIVE!” Muguruza wrote on social media. “Thanks to my expedition and my guide.”

“Special thank you to my guide for keeping me awake when I collapsed at the glacier,” she added. 

Check out more photos of Muguruza’s incredible expedition on Mount Kilimanjaro and follow her journey to the summit on Instagram.