This is the 17206th most frequent Korean word.
서울
"서울" means "Seoul," the capital city of South Korea.
Here, '서울' is used as a proper noun referring to the city Seoul itself.
서울은 한국의 수도입니다.
Seoul is the capital of South Korea.
In this sentence, '서울에서' indicates 'in Seoul', showing the location where actions take place.
서울에서 많은 관광 명소를 방문할 수 있어요.
You can visit many tourist attractions in Seoul.
Here, '서울을' is used as an object of the verb '방문하다'(to visit), showing Seoul as the target of the action.