Palladius System
I recently learned about the Cyrillic transliteration system for transliterating Chinese to Cyrillic based languages, such as Russian, Ukrainian, Bulgarian and other Cyrillic-based languages. The Palladius system (Cистема Палла́дия) was created by Russian Orthodox monk and sinologist Palladius Kafarov in the 19th Century.
A transilteration system is a way of converting text from one writing system into another, like the pinyin in Chinese or romaji in Japanese. In this case its Chinese to a cyrillic based language, such as Russian. This however does not mean that russian speakers learn Chinese using the Palladius system, they actually also use the pinyin tones in the textbooks.
An interesting fact is that this system does not have tones in transliteration. Zhōngguó would be Чжунго, which as you can see doesn't have the tones represented. Instead, it's a context based system, which relies on the context to help determine the meaning. Some may be easy e.g. Шанхай for Shanghai or Пекин for Beijing, but some other words may be a bit more tricky.
This system also does not use "hui" for 会 and other words that sound similar, and instead uses хуэй, which sounds kind of like who-ey, because the russian pronunciation of "hui" is not a very polite word.
Here's how the system works down below: