This is the 8168th most frequent Russian word.
лондон
London.
Here, 'Лондон' is the proper noun for the city of London, used as a direct object in the sentence.
Я мечтаю посетить Лондон в следующем году.
I dream of visiting London next year.
In this sentence, 'Лондон' is the subject, referring to the city as the topic of the sentence's description.
Лондон славится своими музеями и театрами.
London is famous for its museums and theaters.
This time, 'Лондон' is the object of the preposition 'о', denoting the topic of the reported news.