After two years of data collection and mapping images, the City of London Corporation launched Collage, the London Picture Map project, which allows the city’s residents and tourists to see what was once was and no longer exists on the streets of the British capital.

The map contains four main labels. The first is the red ‘C’ markers which represents one image. Meanwhile, the blue circles represent a group of less than 10 images in close proximity and the yellow circles – a group of less than 100 images in close proximity. The red markers mark spots with over 100 images.

“Click on a marker to see the image or images which we have linked to the location. Well known buildings such as Somerset House are likely to have more than one image, so you will be able to browse through a number of relevant results,” the official website reads.

Thousands of historical pictures shown on the digital map - Collage

Thousands of historical pictures shown on the digital map – Collage

“Once you have clicked on a marker to open the image page, you will see that the description includes a note on whether the location on the maps is “exact” or approximate,” the website adds. “Images of streets or buildings which no longer exist can be difficult to place precisely and are therefore usually “approximate.”

Users who disagree with a historical placement of information on a photo can communicate with the developers through the “tell us about this image feature.”

A similar initiative was done in New York City, where software developer Dan Vanderkam along with several others cooperated with the New York Public Library to show what the city looked like in the 1870s-1970s. The NYC site took about 18 months to launch.