Athens has some great nightlife!! There are so many options to choose from, and it really depends on what you're looking for. My personal favourites are rooftop bars that overlook the Parthenon, you can find most of these in Thissio. But many local Athenians would say that these spots are very touristy and not as fun Exarchia and Gazi for example. If you're interested in going to bars that are by the beach, but still pretty close to the city I recommend Gylfada. Psiri it's also a very trendy neighbourhood that is popular amongst the locals! Try them out and let me know what you think!