PhD 0: HKG → SEA, stopover in Seoul

Seoul is the near-optimal stopover from Hong Kong → Seattle

Zoom in:

Of course, actual flight path deviates considering flight route, winds etc.
Stopover in Seoul is great too, with airport (ICN) awarded in SKYTRAX, and free transit tour

Seoul 12 hours stopover

ICN Airport → (AREX) → Seoul station → 南大門市場 → 明洞 → 仁寺洞 → 東大門  →
國立民俗博物館 → 景福宮 → 市政廳 →  Seoul station → (AREX) → ICN Airport

明洞, 不過其實無咩行