Black Water Kingdom (Heishui Kingdom) refers to the Black Water City Ruins (黑水国遗址) near Zhangye, Gansu.
Basic Info

Location: ~17 km northwest of Zhangye city (Ganzhou District), on the west bank of the Heihe River (also called Ruo Shui).

Nickname: “Little Loulan of the Hexi Corridor”.
Status: Major National Historical and Cultural Site (since 2001).
Layout: Two main cities — North City & South City — ~1–3 km apart.
History
4,000+ years ago: Neolithic settlements.
Yuezhi & Xiongnu: Ancient nomadic capitals.

Han Dynasty: County seat of Lede (觻得) under Zhangye Prefecture.
Tang to Ming: Silk Road post station; South City rebuilt.
Late Yuan/early Ming: Abandoned after water cutoff and desertification.
What to see
South City: Better-preserved Ming walls (up to 8–10 m tall).
North City: Older (Xiongnu/Han) ruins, partly buried in sand.
Tombs & relics: Han bricks, pottery, copper-smelting remains.
Landscape: Desert ruins, distant Heihe River, dramatic sunset light.
Visiting
Transport: Drive ~25 min from Zhangye; near G312 highway.
Entrance: Free.
Best time: Late afternoon for golden-hour photos.

