Which city is good to do a PhD in?

I want to pursue a PhD but after spending my Master's in a good lab but surrounded by asocial people in a boring city, I realized the city and the culture will affect my wellbeing more than the research in my PhD. However, I barely traveled abroad and have no idea which cities I should even consider. I'm currently in Europe but I won't hold myself back from some unpopular opinions, such as St. Petersburg in Russia (heard good things about the culture and people there). I basically want to surrounded by interesting and lively people. Where would you suggest?