She’s letting her hair down. Nicole Kidman shared some snaps from her recent Iceland vacation on Instagram, showing off her natural curls in the process. “Beautiful country, trip of a lifetime,” she captioned the photos, thanking Ritz-Carlton Yacht Collection for the experience. In the first pic, the Oscar winner, 59, leans on the railing of the oversized boat, wearing a gray sweater and jeans. In the second, she’s out and about in the same knitwear and black leggings, with her hair blowing in the wind. She’s also seen hugging sister Antonia while dressed in a black Moncler parka and boots. And while not exploring, she took a dip in the…