Simplify the following text for a Grade 11 native English-speaking person.
Original: With the recovery of Babylonian independence , a new era of architectural activity ensued , and his son Nebuchadnezzar II ( 604 â `` 561 BC ) made Babylon into one of the wonders of the ancient world .
Simplified: With the recovery of Babylonian independence , a new era of building followed , and Nebuchadnezzar II ( 604 â `` 561 BC ) made Babylon into one of the wonders of the ancient world .