Sofia (city)

Sofia is the capital and largest city of Bulgaria.

History
Sofia was the location of the members of a particular human trafficking ring who snatched the woman who would become the mercenay known as Sofia at the age of 14 from her hometown of Saint Petersburg

Before joining S.H.I.E.L.D., Natasha Romanoff slaughtered this human trafficking ring in Sofia, while Agent Gennady Markov was investigating them for S.H.I.E.L.D.

Romanoff killed every single member and set the place ablaze, while, unbeknownst to her, the exploited girls were trapped inside and left to die in the fire.

Sofia survived this incident, and grew up to admire Romanoff, wanting to surpass her and claim the mantle of the Black Widow.