The Big Ben Clock Tower
Whether you call it Big Ben (which is technically just the name of the bell) or Elizabeth Tower (which is the actual, official name of the whole structure), this jagged landmark will always be the ultimate picture-postcard image of Britain's capital city. And it was designed by a dying madman.
His name was Augustus Pugin, a prodigy who designed furniture at Windsor Castle when he was just 15. Years later he was hired as one of the designers of the new Houses of Parliament, which had to be rebuilt after the original structures were burnt down in a devastating fire of 1834. Pugin eventually began to lose his mind - possibly due to syphilis, possibly due to mercury poisoning. Prone to violent fits, he was even confined for a time in the infamous asylum known as Bedlam, but somehow found time to create his final and most famous work: the Big Ben clock tower. Shortly afterwards, he succumbed to madness and death.
The Eiffel Tower
An engineering genius and cunning entrepreneur who had previously helped create the Statue of Liberty, Gustave Eiffel did many things - but designing the Eiffel Tower wasn't one of them.
That accolade goes to two of his underlings whose names have been almost forgotten: Maurice Koechlin and Émile Nouguier. They sketched the tower while working for Eiffel's company, and their boss later used his clout and technical innovations to make it a reality.
Many Parisians were horrified at the prospect of a huge metal monolith looming over their city. Many writers, artists and journalists condemned the structure, calling it a "ridiculous tower", a "gigantic black smokestack" and a "hateful column". And as the story goes, one critic made a point of eating lunch in the Eiffel Tower's restaurant every day - because it was the one place in Paris where the tower wasn't visible.
The most iconic military building in the world, the Pentagon owes much of its fame to its shape. And it owes its shape to a farm.
Before the Pentagon existed, the US War Department had a problem. It was rapidly out-growing its offices, and in the 1930s a new complex was put into construction - only to be declared too small even before it was finished. A much larger, flatter building was then planned - it had to be flatter to save on precious steel during the war years. The chosen site was a patch of farmland which roughly resembled a pentagon, so a five-sided building was designed to fit within its borders. The site was then changed, but as it was too late to alter the designs, the pentagon-shaped building was retained. Construction began in 1941. The date: September 11th.
Barcelona's most stunning landmark is the Sagrada Familia, a church which has been likened to an alien ship, a vast termite nest, or a petrified forest. When construction began in 1882 it was intended to be an ordinary Neo-Gothic church. Then the original designer fell out with his masters, and visionary architect Antoni Gaudi took over, bringing a new concept which he knew would take many decades to build. "My client is in no hurry," he said, referring to God.
A devout Catholic, Gaudi was so obsessed with creating Sagrada Familia that he ended up living and working in its crypt. Despite being a celebrity, he resembled a pauper, using pins to hold his ragged clothes together. When he was hit by a tram in 1926, Gaudi was even mistaken for a beggar and left on the street before eventually being carted off to hospital, where he died after devoting the last 43 years of his life to the still-unfinished church. It remains under construction to this day.
The future home of Britain's leaders was built by a notorious rogue, traitor and wheeler-dealer named Sir George Downing. He had served as a diplomat and spy for Oliver Cromwell, vigorously supporting the man who had signed Charles I's death warrant. Then, when the tide turned and Charles II took the throne, Downing abruptly switched sides, betraying former colleagues and amassing piles of cash.
Downing got into the property business, creating a set of townhouses in the heart of London. This became Downing Street, and the properties were built quickly and cheaply. Centuries later, Winston Churchill remarked that the houses of Downing Street were "shaky and lightly built by the profiteering contractor whose name they bear." Before the first Prime Minister Robert Walpole arrived in 1735, private citizens lived on Downing Street - the last one being a fellow named Mr Chicken.