Tower Bridge is a bridge. With towers.
Tower Bridge was first designed in 1780, as a passage from Great Britain to America allowing British soldiers to cross the Atlantic Ocean by foot. However, due to a geographical error, famously blamed on the designers' dangerously high consumption of Peach Schnapps (though it’s hard to imagine how Peach Schnapps can be blamed for anything), the bridge was built over the River Thames instead of the Atlantic Ocean. Many people are noted to have claimed the Atlantic did look a bit small, but they were immediately sectioned and tortured for high treason and insanity. Due to the misplacement of the bridge, the glorious armies of Britain could not stroll over to America. It is for this sole reason that America won its independence.
The towers of Tower Bridge
The two towers that adorn either side of the bridge were originally created as teleportation centres. This idea, however, was abandoned after the designers realised they had not even really gotten to grips with the fundamentals of electricity, and the suggested use of chemicals to realign peoples' molecules only served to turn them into gold. However, the practice of alchemy was by now considered stupid and weird, and was punishable by stoning of the 5th degree.
Now why does that happen…?
Tower Bridge also opens up every once in a while. It is not really known why this happens, but a popular belief is that it began out of sheer terror of the once infamous and mighty Thames Pirates. The bridge opens at least 5 times an hour, providing much entertainment to onlookers as cars plunge into the river and are collected by merchant trade ships, trading in scrap metal and slavery.
Tower Bridge today
Today, Tower Bridge is even more awesome than before. After being visited by Xzibit and the West Coast Customs team in 2004 for the TV show "Pimp My Ride: Extreme Inanimate Object Edition", the bridge has now been hit up with some flames, and also a naked chick riding a motorbike. New rims also came as standard, and even though the bridge had none before, it has been noted, especially by the Queen of England, that the addition is "pimpin' sweet". I couldn't have put it better myself.