Kiev is the capital of Ukraine.
During the late 8th to late 11th centuries, the Vikings raided and traded from their Scandinavian homelands across wide areas of northern and central Europe, as well as European Russia. One of these raid routes took them near Kiev in Ukraine. In the 21st century, this particular route was considered by Skye as one of the possible locations for the Berserker Staff, as Elliot Randolph suggested searching Viking routes for its possible location.
Kidnapping of Nikola
Leviathan obtained the blueprints for a Photonic Amplifier designed by Howard Stark, but as its construction was difficult, they needed a qualified engineer to built it. Leviathan kidnapped a gifted engineer named Nikola in Kiev, taking his family as leverage and imprisoning him at the Red Room Academy to force him to construct the weapon.
Natasha Romanoff reached some of her contacts in Kiev in order to obtain a file regarding the Winter Soldier, that included a photograph of Bucky Barnes inside a Cryostasis Chamber, and notes about his transformation into the Winter Soldier.