I was noticed this pattern about the prepositional case on Twitter. When a place name is the noun in a sentence, it declines. But, when we add a noun such as city, state or country before a place name, then it’s just the noun that declines and the place name stays in it’s original form. I tried all looking online for an explanation about the grammar rule that controls this pattern, but if there is a lesson somewhere online, I’m not finding it. It’s easy enough to memorize the pattern, but I am curious about the reason.
It’s a good notice about the Russian Grammar.
I don’t remember if I wrote about this rule or not.
If not I try to write next week.
But in any case, you have a prepositional in the word before the name, and it’s enough for the language:
В ПетербургЕ - в городЕ Петербург; в “ИзвестиЯХ”- в газетЕ “Известия”;в Нью-ЙоркЕ . в городЕ Нью-Йорк.
It depends on whether the place name is of Slavic origin/has been adopted by the language or not. In referring to the names of Russian towns, both город ‘town’ and the name decline: в городе Москве, в городе Санкт-Петербурге. The names of well-known non-Russian towns decline, whether they stand in apposition to город or not: в Париже, в городе Париже; в Вашингтоне, в городе Вашингтоне. Compare, however, близ города Мэнстон ‘near the town of Manston’ (which is unlikely to be known to Russians and is therefore left undeclined).
The information comes from “A Comprehensive Russian Grammar” by Terence Wade (p.98). It can be found on Google Books.