Answer: 4. The Persians had destroyed it
During the wars between Greece and Persia (480 BC to 479 BC), Athens was destroyed.
After the war in 479 BCE, the Greeks had to rebuild their city, Athens from the ground up because it turned out that Persians had completely destroyed it. The Persian war fought between the Greeks and Persians ended in favor of the Greeks, however, The city of Athens was destroyed in the war.
During the Persian War, the city of Athens was safe from devastation by flood, and this gave a new rise to the new Greek empire and its new look.
The Greeks completely removed all traces of the war and gave their city the lift it deserved after their war.
The destruction of Athens had nothing to do with natural disasters, rather, the Persian War reduced the city to the rubble it became.