The courtyard-well — dvor-kolodets — is a genre St Petersburg perfected: you step through an archway off a grand street, look up, and the walls close into a stone well with a square of sky at the bottom. This is the inner lining of the tenement city, and it's more honest than the facades. Here's where the wells came from, how to hunt for them — and why internet lists of "open addresses" go stale faster than they're printed.

Where the wells came from

The economics of a tenement house were simple: land in the centre was expensive, so buildings went up along the entire perimeter of the plot, wall to wall with their neighbours, leaving a minimal light-well inside. The more profitable the district, the deeper and tighter the wells. Some houses chain their courtyards: archway, courtyard, another archway, another courtyard — five or six links deep into the block. For anyone who's outgrown facades, this is the city's best walk.

How to hunt (worth more than any address list)

Courtyard etiquette

Where it fits in a trip

Courtyard-hunting is the perfect connective tissue between the big items of a St Petersburg itinerary: half an hour of archway exploration between a museum and lunch gives the city a depth no palace can. And if the city's inner lining hooks you, the theme continues in our piece on St Petersburg's communal apartments — the same world, seen from the other side of the front door.

The wells are the city's free, endless and most underrated sight. All you need is curiosity, politeness and the habit of looking up in archways.