St Johns gate Clerkenwell was built in 1504 of Kentish ragstone, and is one of the oldest stuctures in London, and the last of the old gates.
It was orinally part of the priory of St Johns of Jerusalem, that was sacked in the dissolution of the monasteries in the 1530's.
It was the London gateway that William Wallace was bought through on his way to Smithfield for his execution.
The Saint Johns Ambulence was founded here in 1877. It is now a museum and is well worth a visit.