Kypseli, which means 'bee hive' in Greek, is worth noting for its Fokionos Negri section which is a long park like street with many cafes, bars, restaurants and boutiques.
Fokionos Negri is very popular with local residents and to other residents it is a destination for its night time amusements and promenades. You can cruise the strip here in Fokionos! Kypseli Sq is also very nice in a traditional Greek way at the top end of the strip.
There you may get a whiff of old Greece with many people enjoying the outdoors and children playing and so on. Of course non ( or very few) of the people you see in Kypseli will be Greek.
They will likely be Albanian or Ukrainian or Russian or Kurdish or from relatively near by. No big deal these are the people that do all the work in Greece these days. There are some great souvlaki places and restaurants in the square area that should not be missed too!
Also you will find the American chain Pizza Hut. Yawn! Stick with the local cuisine! Try Greek Pizza it really good usually.