Prince Harry and his girlfriend Meghan Markle arrive in Zambia

— -- Prince Harry and his girlfriend Meghan Markle have quietly crossed the border into Zambia during their three week trip in Africa, and Zambia newspapers are reporting the couple is planning to visit Victoria Falls now that they’ve arrived in Livingstone via the Kazungula border.

One of the seven natural wonders of the world, Victoria Falls would be a romantic destination were the prince to propose marriage. Situated between the border of Zambia and Zimbabwe, the 354 falls along the Zambezi River can be seen via helicopter tours that give an unrivaled view of the plunging water -- an ideal way for the couple to view the sight privately.

The couple landed in Botswana three weeks ago to celebrate Markle’s 36th birthday, and speculation has swirled that the fifth in line to Britain’s throne is likely to pop the question in what he has described as the prince’s "second home."

Prince Harry, Meghan Markle arrive in Botswana for birthday vacation

Earlier this year, Harry shared that Botswana will always have sentimental value to him, saying, "I first came in 1997, straight after my mum died. My dad told my brother and me we were going to Africa to get away from it all."

"This is where I feel more like myself than anywhere else in the world," he said. "I have this intense sense of complete relaxation and normality here."

In 2016, Harry said he hoped to share Africa with his children one day.

"I have this love of Africa that will never disappear. And I hope it carries on with my children as well," he said.

Prince William proposed to Kate Middleton atop Mount Kenya in 2010.

Prince Harry is due back in London this week for an event on Wednesday on the eve of the 20th anniversary of his mother Princess Diana's death, where he and his brother will make a special visit to the Kensington Palace memorial sunken garden to pay tribute to their late mother.

Prince William, Prince Harry to honor Princess Diana at garden ahead of the 20th anniversary of her death

The brothers, accompanied by Princess Kate, will view the special garden, which has been transformed with their mother's favorite white blooms to commemorate her life.