When in 1930 the Piccadilly Line began to stretch northwards towards Cockfosters, twenty-two tunnelling shields were mustered for the underground work. In the process some of the most memorable underground stations were built under the influence of Walter Gropius and the Bauhaus movement; the bold cylindrical or rectangular shapes, as, for example, at Arnos Grove and Sudbury Town, became instantly recognisable as portals to the underworld.