Between the NYPL, the MCNY, the Municipal Archives, the Library of Congress, and countless other resources holding images from New York City's past, you could almost visually recreate an older version of the city on your desktop. That's pretty much what one man—software engineer Dan Vanderkam—has done, using the NYPL's massive database of images.

OldNYC is almost overwhelming in size, placing tens of thousands of historic images over a map of New York City, allowing you to step back to a time when your Chase Bank was shoe cobbler, and your Duane Reade was a speakeasy. Just click on an address or intersection and you'll see How Things Used To Be. The map doesn't include modern day images, but you can compare on your own—here's 345 Madison Avenue in 1923, versus today.

345 Madison Avenue (via NYPL and Google Maps)

Most of the photos are from 1924 to the 1940s, culled from the work of photographer Percy Loomis Sperr. Imagine how much more time you'd spend in the past if Berenice Abbott's photos from the 1930s were added. And maybe we need a separate map that just brings us back to the 1980s.