Sorting photos in preparation for exhibitions, I came across these two snapshots. One is taken 2004 and shows workers doing maintenance work at the Sheshan Observatory. When they saw me climbing around the roof with a camera, they posed for a photo, as if they knew (they didn't) there is a similar photo dated 1899 which is hanging in the Observatory Museum, literally below their feet.

Builders at the Sheshan Observatory, as seen in 2004.

A picture of builders of the Sheshan Observatory from 1899, as seen in the Observatory museum in 2004.