You probably know about the crooked Tudor buildings of Staple Inn on Holborn. It's not the only local survivor of earlier centuries, however. Look for an opening, a few doors down to the east, where a heavy pediment bears the sign of the Mercers' Maiden. It leads into an alley, where your footsteps echo off the glazed tiles, and thence into a small courtyard. Here you will find Barnard's Inn Hall.
The hall dates from the 15th century, when it was used as an Inn of Chancery. Its job was to train up law students who would later enter the Inns of Court. The hall is one of only a handful of buildings in the City to survive both the Great Fire and the Blitz. The space is both compact, and impressive, like a grandiose school hall. It served exactly that purpose from 1888 to 1959, when Barnard's Inn was occupied by Mercers' School.
Since 1991, the hall has been home to Gresham College, which also boasts a long, proud history. The college is London's earliest institution of higher education. Ever since its foundation in 1597, it has offered free lectures to the public. Today, you can enter this magnificent half-timbered hall and learn about the chances of life on other planets, or Britain's relations with Korea, or the origins of marine insurance. The programme of free lectures covers a wider range than just about any other institution.
You can't pre-book for these talks — just turn up and wander in. This sometimes means that the hall fills to capacity, so proceedings can also be streamed to a second room down in the basement. This lower area holds its own marvels. A white linen damask cloth used by Elizabeth I and embossed with her symbols is displayed in a cabinet — it looks as fresh as new. In places, Roman stonework can be found, and there are rumours of an old passageway that once linked up to neighbouring buildings. During the 1780 Gordon Riots, the room was flooded with gin from an adjacent distillery, which had been pummelled by rioters.
You can view the building for yourself, free of charge, on any day when a Gresham lecture takes place. The more obviously popular talks are now held in the Museum of London, which has greater capacity, but it's worth heading along to one of the Barnard's Inn talks to see this remarkable survivor in all its dark-wood glory. And if you can't make it to The Square Mile, most lectures are recorded and uploaded to the website. For updates, follow on Twitter (@GreshamCollege), or Facebook.