Many people have been intrigued by interesting coins since childhood. I started a collection when I was eight, and every accidental Bicentennial quarter, wheat penny, or elusive Canadian dime that I came across in my spare change made it into the collection. My collection has only grown as I have started traveling all over the world and encountering much more impressive currency, but there are some coins and bills out there that are even more interesting. Here are five of the most unique currencies from around the world (from both the past and the present) so you can start your own collection.

Australia's Waterproof Banknotes

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With cash, there is always the threat of counterfeiting, so Australia decided to change the game. Instead of the paper-like banknotes that are used in most countries, Australia's money is made of polymer, which gives it the texture of wax. Not only does this make it extremely difficult to fake, but it also makes the bills waterproof, so you never have to worry about accidentally leaving them in your pants pocket and sending them through the wash. As if that wasn't cool enough, the $5 banknote features a sort of optical illusion effect, in which it looks like a bird is flapping its wings on the back of the bill as you move it.

Africa's Headless Zaire

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In 1997, the leader of the country of Zaire (now referred to as the Democratic Republic of the Congo) was overthrown. President Mobutu's face just happened to be on all of the money in the country, however, so the government faced a real problem. There was a shortage of cash while new bills were being printed, so they came up with a rushed solution that would make a lot of lazy third graders proud: they simply punched a hole in the paper where the president's head was on the old bills and continued to use them until the new bills were ready. Problem solved!

Aruba's Colorful, Animal-Covered Florin

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It is hard to find a currency that you wouldn't want to spend, but Aruba's current set of Florin is so beautiful that you will be tempted to frame it instead. Each denomination of money features a different animal native to the island and a different color. The designs are taken from pre-Columbian pottery, so that the money ties together the past and the present. Some of the animals featured are rattlesnakes, frogs, owls, fish and conch shells.

China's Tea Bricks

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For nearly as long as history books can remember, Asia has been associated with tea. This is why it is no surprise that in the 19th century, China, Tibet and Mongolia all used tea bricks as a form of currency. To make the tea bricks, different types of tea leaves were pressed together into one block. The better the quality of the tea leaves, the higher the value of the tea brick, which was used to buy such things as clothes, livestock, or even to pay off debts. While you might be wondering what the recipient of these tea bricks would want with a bunch of tea instead of money they could use to buy something else, rest assured that this was a preferred method of payment. You can't make tea out of metal coins!

Canada's $1 Million Dollar Gold Coin

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Coming in at number one on the list of most unique currencies is the "world's largest legal tender." This golden Canadian coin is made out of almost 100 percent pure gold bullion and weighs a whopping 220 pounds. The coin, worth one million dollars, is so heavy (and so full of gold) that it sells for more than twice the value on its face, meaning that at any given time it can be sold for more than $2 million regular Canadian dollars depending on the current value of gold. Good luck carrying that around in your pocket!