The foundation stone of Prague’s oldest bridge, named as "Charles Bridge" or "Karlův most" in Czech, was laid down by Emperor Charles IV on 9th July 1357 at 5:31 am. This exact time was very important to the Holy Roman Emperor because he was a strong believer in numerology and felt that this specific time, which formed a palindrome (1357 9, 7 5:31), was a numerical bridge, and would imbue the bridge with additional strength.

The bridge was completed 45 years later, in 1402. It is made of sandstone blocks, 515.76 m long, 9.5 m wide, and rests on 16 vaults of different spans reaching from 16.62 m to 23.38 m. It is flanked at each end by fortified towers (Lesser Town Bridge Towers, Old Town Bridge Tower). From 1683 to 1928, 30 statues of saints were carved to decorate the bridge, the most famous of which is the statue of St John of Nepomuk.

From 1883, there was a horse tram passing across the bridge, replaced in 1905 by an electrical line. In order to preserve the artistic view of the bridge and not to ruin it by wires leading at the top, Frantisek Křižík devised a special line through the bridge deck. Yet the heavy carriages vibrated and damaged the construction, and thus were replaced by buses in 1908. Even the buses were not ideal, so the transport was again stopped the next year, to be renewed in 1932 using pneumatic buses. Public transport crossed the bridge until WWII, and cars stopped driving across the bridge in 1965. Only pedestrians can cross it now.

More Info: en.wikipedia.org