When I am writing blog or Facebook posts, or captioning photos, I have a choice between writing, for example, Gyeongbokgung Palace, Gyeongbokgung or Gyeongbok Palace. gung (궁) means ‘palace’ in Korean, so Gyeongbokgung Palace is redundant, but is probably the best choice as it gives the full name in Korea plus tells English-speaking readers what it is. Gyeongbokgung is good Korean but not helpful for English speaking readers. Gyeongbok Palace is possible, but just looks and sounds awkward.
Some geographical and building words work better and worse: Jejudo and Jeju Island and both used, while no-one uses Jejudo Island.* Yeouido in Seoul is always thus, never Yeouido Island or Yeoui Island (possibly helped by the fact that it’s now for practical purposes joined to the shore) (and I note that the Wikipedia article says ‘Yeouido (Yoi Island or Yeoui Island)’. Seoraksan and Seorak Mountain are both used, but not Seoraksan Mountain (or Mt Seorak). Namsan yes, Namsan Mountain ?, Nam Mountain no.** (Wikipedia says ‘Nam Mountain (pleonastically Namsan Mountain or Mount Namsan)’.) Hangang yes, Han River yes, Hangang River no. Bukhansanseong yes, Bukhansanseong Fortress maybe, but that’s probably because the name is so long, with four separate syllables/morphemes, Bukhansan Fortress yes.
I am probably inconsistent with my usage, depending on my intended readership. I probably add the English words less in this blog than I do on Facebook. I could translate Gyeongbokgung as ‘Fortune Palace’, but that wouldn’t be helpful.
*There is a complication here: do means both ‘island’ and ‘province’ (two different Chinese words). Jeju-do Province (officially Jeju Special Self-Governing Province) includes Jejudo Island plus numerous smaller islands. (Yes, I used ‘Jejudo Island’ there for clarity.)
**Because Namsan (South Mountain) is such a generic name, it has to specified unless the context is clear. I have photos from Namsan Seoul and Namsan Gyeongju (or Seoul Namsan and Gyeongju Namsan. (Wikipedia lists seven Namsans.)