An eccentric English aristocrat who constructed a 20-mile network of underground corridors to avoid coming into contact with his fellow humans on his country estate; a Japanese dentist who has amassed an enormous collection of decorative details from buildings spanning a century, retrieved from Tokyo demolition sites; the German inventor of ‘Scalology’, who has spent 60 years studying staircases; and Inuit soapstone carvings of a Cold War early-warning station and of an airport terminal are among the surprises offered by the 14th Venice International Architecture Biennale.