Feeling adventurous? Feeling wreckless? These are the sort of activities your bored-but-daring friends will egg you on to do and if everything goes to plan you'll have the time of your life. Here are a few mental activities you might be tempted to try out next time you are away from the office and looking for an adrenalin rush. But if you do, know this, your travel insurance probably won't cover it. Some of these activities are so extreme that should something go wrong and you did have coverage, it would be your next of kin doing it on your behalf!

If you've never seen The Northern Lights then you can not possibly understand what you're missing out on. And if you have seen them, you know that you'll probably never see anything quite like them again in your life. These natural light displays are better than any man-made laser light show that you've ever been to see. The colours that come out during their nightly performances (primarily reds and greens) look like nothing that should be in the sky and yet are so stunningly beautiful that you're sure they were meant to be there. Seeing the Northern Lights is a magical experience and one that can be done from several different picturesque parts of the world.

Most people are content to spend their lives achieving modest but realistic goals. They aim to rise towards the top of their business or to do well at the gym in the sport of their choice. And then there are the people who aim for more. These are the people who don't just run marathons but are ultramarathoners, the people who don't just walk regular buy actually walk around the world. What drives these people to do what they do? Maybe it's an internal urge to be the best at something. Or maybe they're just plain crazy.

Some of the most fascinating man-made structures on earth are the massive auditoriums that were once used for theatrical performances, music shows, as well for more sinister purposes such as violent wild animal shows and gladiatorial contests. These awesome theatres have a historical stigma attached to them, and in some cases, history is still being made because some are still being used today.

It's hard to believe that some of these theatres are close to 3,000 years old, and it's amazing that they're even still standing. The amount of engineering knowledge that our ancient ancestors had developed is just as mesmerising especially when some of these auditoria rival present-day outdoor theatres in terms of acoustic properties. That's amazing for a 2,000 year old theatre that is large enough to seat 25,000 people or more!

Green is the new black and cities are the new celebrities. Industries across the nation from electronics to oil are moving forward with eco-friendly plans designed to show their support of the environment (and to put dollars in their pockets from eco-conscious consumers). Local government and business initiative are pushing onwards with the development of ecocities (or sustainable cities) as a viable alternative, and they're rapidly becoming the trendiest new place to lay down your roots!