This code will set $allowed_city to "yes" if request made from Ukraine (or any other allowed country) OR from Krakow (or any other allowed city).

In /etc/nginx/nginx.conf:

        geoip2 /path/to/GeoLite2-City.mmdb {
                $geoip2_data_city_name          city names en;
                $geoip2_data_country_iso_code   country iso_code;
        }

        map $geoip2_data_country_iso_code $allowed_country {
                default no;
                UA      yes;
        }

        map $geoip2_data_city_name $allowed_city {
                default $allowed_country;
                Krakow  yes;
        }