"What's the most beautiful place you've ever been?" I once asked a friend who had married a billionaire heir. She was constantly on her dad's private jet and it looked like she had been almost everywhere. Her answer was immediate: Sardinia. After seeing the photos on Instagram, I knew I had to go one day. The water looked almost fake. Turquoise fading into cerulean, framed by enormous granite rocks and stretches of white sand that looked more li…