I have previously visited the Netherlands, Belgium, France, Luxembourg, Switzerland, Spain, Italy, Germany, Austria, Czech Republic, UK, and Ireland in Europe. So most of western and central europe.
This time I've to visit Copenhagen for a 3-day conference in September. So I will spend at least 3 nights there, out of which 1 day will probably go completely to the conference and the rest 2 days I might get time to see the city.
Where else should I visit on my European trip this time?
I am thinking of visiting maybe 4-5 new countries on this trip. I can have up to 20 days for this total trip, with some days before the conference and some days after the conference.
What are some options that you can suggest to me based on the time of the year. My budget range for the whole trip will be mid, let's say about 3000 euros for 20 days. I would prefer to use public transportation, trains, and hostels for my stay.
Also, is there possibility of seeing northern lights in mid September or should I leave nordics for the future? I will be flying solo from India and will be on a single entry Schengen visa.
Any important festivals or celebrations around this time of the year that I should totally experience at least once in life? Something kinda Oktoberfest.