Prince William and Kate Middleton on Ski Vacation

Prince William, 25, and girlfriend, Kate Middleton, 26, hit the slopes last week in the Swiss resort of Klosters – a favorite of the British royals and the place where the couple were first revealed to be seriously dating four years ago.
This year, Middleton looked more comfortable than ever in the royal fold as William's father, Prince Charles, arrived at the resort on Thursday night and joined the pair skiing on Friday and Saturday. Middleton's inclusion in family events adds fuel to speculation that William – second in line for the throne after his father – could one day make her his princess bride.

The night before Prince Charles arrived in town, the couple got some partying out of their system as they hit the resort's pricey disco, Casa Antica, with friends.

Throughout the week, onlookers watched as the young couple flirted, giggled and touched affectionately. They rode ski lifts together, stuck by each other's side as they swooshed down the mountain.
"They were out on there [on the slopes] together. They looked like they were having a nice time," one onlooker tells PEOPLE. "At one point they had a little cuddle."

Their routine never wavered even as blinding snow, strong winds and icy temperatures hovering around zero made ski conditions difficult. They would ski all morning and have lunch at one of the many restaurants dotted around the mountain resort – including a pizzeria one day.