Plovdiv Old Town (Stari Grad)

Plovdiv is Bulgaria's second-largest city and has been recognized as one of the oldest settlements in Europe, with evidence of habitation reaching as far back as the 6th millennium BC.

Bulgarian is the official language of Bulgaria, where it is used in all spheres of public life.

The difference for me is mainly that Plovdiv feels like a little holiday in the sun, while Sofia feels like an energising city break. But, ultimately, they're both awesome cities and well worth a visit. And as Plovdiv is only around 90 minutes from Sofia down the motorway, you can easily do both in one trip.