Well this isn't a needle, and it has nothing to do with Cleopatra. It's actually an obelisk from Egypt that is 3500 years old (quite a bit older than London itself in fact). The obelisk was originally erected in Heliopolis in 1500 BC. Cleopatra's Needle arrived in England in 1878. The Victorians wanted to celebrate a victory over Napoleon almost 70 years earlier. After being given this obelisk by Mohammed Ali (no, not the boxer...) the Viceroy of Egypt.

A special boat was built to carry the obelisk back to Britain from Egypt. The journey was very difficult, and 6 men drowned in the process, and at one point the boat had to be cut free and disappeared for a while in very stormy weather.

Eventually it was found again and was eventually erected on the side of the Thames (almost opposite the London Eye). These days however, most people probably don't even know why it's there even if most people know of it. The second picture shows the plaque.

Official statement

First erected in Egypt, by Pharaoh Thotmes III around 1500BC, Cleopatra's Needle was given as a gift to the British people in 1819, in recognition of Admiral Nelson's victory over the French fleet, at the Battle of the Nile in 1798.

Opposite the Victoria Embankment Gardens, on the river front, Cleopatra's Needle is flanked by magnificent bronze lions. The 68 1/2 ft. monolith sits on a pedestal containing various momentous objects including: standard foot and pound, a full set of British Empire coins, Bibles in various languages, a railway guide, an almanac, and copies of contemporary newspapers

"Cleopatra's Needles" is the name given to two Egyptian obelisks, formerly at Alexandria. One of these obelisks now lies in New York, Paris and London.

They are made of the rose red granite of Syene, and were originally erected in front of the great temple of Heliopolis, where Moses was born.
The obelisks were taken to Alexandria shortly before the commencement of the Christian era after the death of Cleopatra, but possibly in pursuance of a design originated by her.

• Directions: nearest tube : Embankment and head downstream
• Address: North side of Thames