The Shadow Reckoner
Recover a vanished landmark's shadow the way Holmes recovered the elm's — by proportion.
The elm was gone, so Holmes scaled its shadow from a fishing rod: like triangles, no more. Enter any landmark's height and a measuring stick's shadow to cast the lost shadow yourself.
Drawn from The Musgrave Ritual (The Memoirs of Sherlock Holmes, 1893) — read the summary & analysis, or try Walk the Ritual, this story's game. More at the Game Room and the tool bench.