Busloads of visitors stop at Km69.8, where a tall, white monolith marks the Tropic of Cancer, though probably, before seeing it, few had ever stopped to wonder much about that line's geographical significance. In fact it marks the line of latitude, 23°26'N, at which the sun is directly overhead at noon on the summer solstice (the year's longest day, 21 or 22 June).
The monument actually looks most photogenic from around 1km further south with layered green ridges set behind it. Further south still, notice the boat-shaped church in Zhangyuan, just 40m west of the road at Km74.
