Once you're over 30, you've missed your chance to get a working holiday visa to Australia, so this is definitely a trip to fit in during your 20s. The visa lets you stay in the country for 24 months, doing casual work while you're there. If you're going to see Australia properly, you'll probably need that long to work your way around the continent. But it's not just visas you'll miss out on if you wait until you're 31...
In pictures: the world's most secluded beaches
Halloumi and herbs: eating your way around Cyprus
In pictures: 17 irresistible island retreats
Twenty-five capital cities to see before you die
Maltese delights: learning to dive in Malta