London's Guildhall sits on top of a Roman amphitheatre. Beneath the art gallery next door lie the remains of Londinium's arena, the largest in Britannia, its outline traced in black paving stones across the yard.

The Saxons appear to have built their first hall directly over the Roman ruins. By the 1440s, stonemason John Croxton had raised the Gothic structure that still stands today, complete with a porch in a style once optimistically called 'Hindoostani Gothic.'

Inside the entrance hall, two wooden giants named Gog and Magog keep watch. The current pair date from 1953, replacements for an older set destroyed in the Blitz. Dickens, as a boy, made them his first destination when he set out to seek his fortune.

VoiceMap's self-guided audio tours trace the Guildhall's layers, from the amphitheatre fragments in the gallery basement to Dickens's childhood pilgrimage to the giants, connecting Roman Londinium, medieval guild politics and the livery companies that still elect the Lord Mayor.