St John Street, Islington, was originally a lane linking the village of Islington to the City of London.
When you look up St John Street (as in the pic above) you can see a slight incline. That's been made up of gravels from the ice age. Underneath that is London clay. Where the gravel and London clay meet there is a line of fresh water springs.
Those springs are still evident in place names such as Sadler's Wells and Clerk's Wells, more commonly known as Clerkenwell today.
The geology has had a really important influence in the way this area started to develop.