Prague flourished during the 14th-century reign (1346–1378) of Charles IV, Holy Roman Emperor and the king of Bohemia of the new Luxembourg dynasty. As King of Bohemia and Holy Roman Emperor, he transformed Prague into an imperial capital and it was at that time the third-largest city in Europe (after Rome and Constantinople).
He ordered the building of the New Town (Nové Město) adjacent to the Old Town and laid out the design himself. The Charles Bridge, replacing the Judith Bridge destroyed in the flood just prior to his reign, was erected to connect the east bank districts to the Malá Strana and castle area. On 9 July 1357 at 5:31 am, Charles IV personally laid the first foundation stone for the Charles Bridge. The exact time of laying the first foundation stone is known because the palindromic number 135797531 was carved into the Old Town bridge tower having been chosen by the royal astrologists and numerologists as the best time for starting the bridge construction.In 1347, he founded Charles University, which remains the oldest university in Central Europe.