If you're looking for some bank-breaking works of less-than-staggering genius, look no further. Not only were these five leaders plagued by terrible ideas, they never bothered to get their money's worth.

1. Caligula's Bridge (Over Very Troubled Waters)

As he was going mad, the Roman emperor Caligula began spending money on increasingly bizarre and extravagant projects to satisfy his megalomaniacal whims. Among Caligula's best efforts: constructing a three-mile pontoon bridge across the Bay of Naples by confiscating merchant ships, having their bulwarks sawed off (making them useless afterward), spreading soil over the planks, and then planting trees, shrubs, and flowers to make the bridge more pleasant. When it was done, Caligula supposedly rode his horse across the bridge at the head of 20,000 troops to prove wrong an earlier prophecy that claimed he could no more become emperor than ride across the bay. After a night of partying, Caligula left and never came back. The bridge itself was destroyed by a storm a short while later.

2. Nero's Extreme Home Makeover

As the noted gossip Suetonius tells it, the emperor Nero decided to go Caligula one better by building an extravagant mansion for himself in burned down neighborhoods of Rome following the great fire of 64 CE. Called the Domus Aurea, or "Golden House," because its exterior was overlaid with gold leaf and mother of pearl embedded with gems and beautiful seashells, the building was far and away the largest private residence ever seen in Rome, covering a large part of three of Rome's seven hills. So, just how extravagant was Nero's crib? In the entrance hall stood a 120-foot statue (of Nero); a columned arcade ran for a mile; a pool the size of a small lake was surrounded by buildings shaped like cities and fake farms; exotic animals roamed everywhere; and the ceilings were carved ivory panels that could retract to allow a rain of perfume and flowers to fall on partiers. The Roman poet Martial said of it, "One house took up the whole city of Rome." When it was finished Nero famously said, "Good, now I can at last begin to live like a human being." [Image courtesy of Ryan Freisling.]

3. Prince of Thieves (Mainly the White-Collar Variety)

Prince Jefri Bolkiah, the brother of the sultan of Brunei, spent his small country into bankruptcy during the 1990s with a multibillion puts all the other royal contenders to shame. Clearly, Prince Jefri knew how to treat himself right, as the 300,000 citizens of Brunei found out when his purchases were put up for auction as part of bankruptcy proceedings (pictured, courtesy of the BBC). Included for sale were a golden toilet roll holder, rows of gold plated Jacuzzis and showerheads, porcelain flamingos, gold plated wastepaper baskets, a multi-million dollar marquee complex, Comanche helicopter simulators, an Airbus jet, a Formula 1 racing car, and a bronze plated eight-foot-high Trojan horse. Luxury hotels in Great Britain, France, and Singapore were also favorite purchases of Jefri. That's not to say he hasn't been caught with his fingers in more than a few (illegal) pies. Previously, a lawsuit had been brought against Jefri for the theft of approximately $16 billion from Brunei's state run economic development agency. Needless to say, he didn't develop anything profitable with the funds.

4. Versailles and Everything After

Louis XIV was one of the most extravagant kings in French history. A lot of the stuff Louis spent money on was quite respectable—as a famous patron of arts he supported literary and cultural figures like MoliÃ¨re, Le Brun, and Lully, and he spent a great deal of money to improve the Louvre. Of course, Louis' most famous boondoggle was his palace at Versailles, a sprawling 700 room rococo residence on an 800-hectare estate with carefully tended gardens and woodlands about 15 miles to the southwest of Paris. In fact, Louis used so many luxurious materials—including gold leaf, crystal chandeliers and doorknobs, silk and satin window dressings, exotic hardwood furniture, ivory, mother of pearl, and precious stones—and his house contained so many famous works of art, that it's actually impossible to calculate a modern cost equivalent. If the spending wasn't bad enough, Louis also foolishly kicked out the Huguenots, or French Protestants, even though they provided many of the country's leading merchants and much of its tax income. Last but not least, Louis launched an endless series of unwinnable wars that were to put the last nail in the coffin of French finances. Who knew the nickname the Sun King referred to one that was setting? [Image courtesy of Eric Pouhier.]

5. Empress Dowager's Ship That Never Sailed

In 1888, China had been on the ropes for a good three decades. Once an international powerhouse, the nation's world rep had suffered greatly since its humiliating loss to Great Britain in the Opium War. Foreign technical advisors told the mandarins who set policy that China needed a modern navy along Western lines if it was going to defend itself from further European and Japanese aggression, and the mandarins duly set aside 30 million taels of silver for new, modern ships. However, the dowager empress Cixi, who had the final say, decided that the money would be better spent on reconstructing the elaborate Summer Palace, which had served as a vacation spot for the Chinese imperial family for millennia.

When advisors complained that the only ship she had purchased was a marble pleasure yacht, she noted that while it was indeed immobile, "it's still a very nice place for a picnic."

Ed. Note: This list was pulled from Forbidden Knowledge.