Although you do not clarify when you intent to do it, I will assume is for any time during the year. In this case I will suggest Thessaloniki, Greece. It is a rather large city and it has very interesting places in and around it that are worth visiting. The town itself has a lot to offer and it is well known for its culinary treats and its pastries.
Close by is Vergina, where the grave of Alexander the Great's father can be seen along with other findings.
Also if you like something really unusal, that is a visit to Mount Athos. That can be one in a lifetime experience. To do that you have to obtain a special permit by the Offices of the Monastic Community located in Thessaloniki. You are allowed to spend a few days in a monastery as a guest and you have to follow their way of daily routine.
On the links below there are very interesting tips and Information should you decide to go ahead. I strongly suggest if you are so incline for the extraordinary to go ahead and go there.
All places in Europe have lots of history, pet.
Be advised that the further off the beaten track you go, the less likely you are to find people who can speak English.
Gotland Sweden.
Transylvania in Romania. Brasov and the surrounding area are amazing and there are very few tourists. We then did a farm stay at a farm about an hour away from Brasov in a small Hungarian-speaking town where there were no tourists at all.
https://www.google.com/search?q=brasov+r...
