This is the 2123rd most frequent Russian word.
токио
Tokyo (the capital city of Japan).
Here, 'Токио' is used as a proper noun representing the capital city of Japan.
Я мечтаю поехать в Токио.
I dream of going to Tokyo.
In this sentence, 'Токио' is again a proper noun, used to refer to the geographic location impacted by the typhoon.
На Токио обрушился мощный тайфун.
A strong typhoon struck Tokyo.
Here, 'Токио' refers to the city as a singular entity for which a map is needed.