Yunhee J. answered 07/26/21
Experienced Korean Language Tutor 10+yr private lessons, Korean School
Others explained it well. One thing I want to add is that 동경/북경 were more commonly used for older generation. These days 도쿄/베이징 are used among younger generation.
Some of the same examples off of my head are
불란서 - 프랑스
나성 - 로스엔젤레스