Here's an idea perfect for the family historian-slash-photographer.
Click on a link, then move the slider to segue from past to present.The idea was to revisit historic photograph locations and take identical photographs, as if the camera never moved and the world changed around it. It's a little more difficult than I expected due to variations in lenses, inaccessibility of locations and a lack of constant markers. Still all of these are close to correct (some are better than others). [Link, via Neatorama]

Very cool! Like doing a time travel.
I would imagine that it's infuriatingly difficult to get exactly the right angle and vantage point. But, with digital cameras it costs next to nothing to take and delete dozens of lousy pictures.
Wow thats interesting. But how do you make the slide effect?
Lisbeth (from Denmark)
Lisbeth,
There's a slider in the upper left-hand corner of each of the linked pages (like this one). Just drag it back and forth to see the effect.
Chris
I'm aware of that - but what technique lies behind?
Lisbeth
Sorry, it's accomplished this piece of Javascript code, and a little more on the page itself.
Thanks Chris!
It's very nice.
Lisbeth