The spacious estate, Althorp House, which has been in the Spencer family for more than 500 years, is also where Charles' sister Princess Diana was laid to rest.
Karen took to her Instagram Stories on Sunday, where she shared a serene image of the Oval Lake, close to where the late Princess of Wales is buried.
According to the BBC, the Earl was the one who decided his sister should be buried at the grounds of his home, which is where they both grew up.
The initial plan was reportedly for Diana to be buried in the family vault at the local church, but due to security and privacy concerns, Charles instead decided instead to lay her to rest on an island at the centre of the property's oval lake – a view which the family has long kept private.
While members of the public can visit the property when it is open in the summer, they are unable to gain entrance to the island.
The decision came following the family's horror at the press intrusion experienced by Princess Diana, with Charles movingly calling his sister "the most hunted person of the modern age" in a gut-wrenching eulogy at her September 1997 funeral.
Charles also paid tribute to his beloved late sister as the "very essence of compassion, of duty, of style, of beauty," and summed up the nation's horror at her tragic death when he called himself: "the representative of a family in grief, in a country in mourning, before a world in shock".
On the most recent anniversary of her death, he posted a picture on his Instagram account that showed a young Diana standing with her arm around Charles' shoulder, as he smiled up at the camera. He didn't add a caption, allowing the image to speak for itself.
In Prince Harry's tell-all book Spare, he detailed how he and his wife Meghan Markle took a boat trip to pay their respects to his late mother.
All didn't go as planned during the secret visit however, as the small vessel apparently got stuck in the mud but luckily Diana's brother was on hand to give them "a little push" so they could make it to the land in the centre of the lake.
Prince Harry also explained that he had wished to be buried alongside his mother on the island of the lake but that was not deemed possible.
Instead, the Prince has chosen to have his body laid to rest at Frogmore House, which is where he celebrated his wedding to Meghan.
Charles and his wife Karen often share updates from the iconic residence and the Lady of the House even has a weekly newsletter where she updates fans on renovations at the historical home. Recently, Karen revealed they have made an exciting discovery at the lake – uncovering the footings for an old boat house underneath the mesmerising water.