The area of London known as Clerkenwell plays an central role in WHERE THE DEAD LIE, #12 in the Sebastian St. Cyr series (coming in the spring of 2017). I'll have more to say about the area in the future, but today I'm just concentrating on St. John's Gate.
Built in 1504 as the entrance to the Priory of the Knights of St. John--the Knights Hospitallers--it is one of the few parts of the monastery still in existence. At one time it was the workplace of Samuel Johnson; it was also the childhood home of William Hogarth, whose father opened a coffee house there. This is what it looked like in Sebastian's day (as seen from the south side; the photo above is taken from the north):
It isn't anywhere near as solid as it looks. Built of brick surfaced with stone, it was in pretty bad shape by the end of the 19th century--as this late 19th century watercolor below clearly shows:
Thank heavens someone realized its value and rescued it in the nick of time. What you see today is heavily reconstructed. But it's actually pretty amazing that it's still standing.