Yantai

Fushan Tunnels

Cold War sub tunnels near Qingdao.

Red Beach / Honghaitan (红海滩)

Coastal wetland in Dawa District, Panjin (Liaoning) whose tidal flats turn vivid red each autumn from Suaeda salsa, an alkaline-tolerant plant. Within Asia's largest reed marsh; state-level nature reserve. Best mid-September to late October.

Panjin, Liaoning. Best in Sept-Oct — your dates work — but ~7h from Beijing.

Museum of Evidence of War Crimes by Japanese Army Unit 731

Former secret Japanese biological/chemical-warfare facility in Harbin operating 1933–45 that conducted lethal human experimentation. Part of the site is preserved as a public museum memorializing the victims.

Harbin. Heavy historical weight, far north.

Harbin International Ice and Snow Sculpture Festival

Annual winter festival in Harbin, Heilongjiang, billed as the largest ice and snow festival in the world. Massive illuminated ice sculptures carved from Songhua River blocks. Late December to late February.

Harbin in JANUARY. Wrong season.