Archaeologists examining the remains of the city of Babylon have found what appears to be the foundation of the tower: a square of earthen embankments 91 meters on each side. The tower's most splendid incarnation was probably under King Nebuchadnezzar II who lived from 605-562 BC. The King rebuilt the tower to stand 91 meters high. According to an inscription made by the king the tower was constructed of "baked brick enameled in brilliant blue". The terraces of the tower may have also been planted with flowers and trees. 
The tower, referred to by the Babylonians as Etemenanki, was only one of the marvels of the city. The final beginning of the end of the tower of Babylon probably began around 478 BC. The city had been taken over by the Persian King Xerxes who crushed a rebellion there that year. The tower was neglected and crumbled.
Although the Tower of Babylon now gone, a few lessor ziggurats still exist. The largest surviving, although damaged, temple is now found in western Iran, in what was once the ancient land of Elam. It is located about 29 km from the capital of Elam, a city named Susa. Built in 1250 BC by the King Untash-Napirisha it once had five levels and stood 52 meters in height.
What we know about the Tower of Babylon today comes only from the little archaeological evidence found and a few ancient writings. Nebuchadnezzar described how "gold, silver and precious stones from the mountain and from the sea were liberally set into the foundations" and how to rebuild it he called on "various peoples of the Empire, from north and south, from mountains and the coasts" to help with the construction.
Even in 460 BC, after the tower had been crumbling for many years, the Greek historian Herodotus visited the tower and was very impressed. "It has a solid central tower, one furlong square, with a second erected on top of it and then a third, and so on up to eight. All eight towers can be climbed by a spiral way running around the outside, and about halfway up there are seats for those who make the journey to rest on".