Coimbra's Porta de Barbacã once guarded the medieval city against anyone bold or foolish enough to approach uninvited. A moat ran in front of the arch, traces still lurk in the Góis store's basement next door and just behind it, above the Tower of Almedina's gate, sit two small holes with the cheerful name Mata Cães, literally 'dog killers,' through which defenders poured boiling oil on attackers.

The arch itself is modest, easy to walk past on the busy pedestrian street Rua Ferreira Borges. Step through, though, and you cross the threshold that separated downtown merchants from the walled old town for centuries.

VoiceMap's self-guided audio tours use the gate to mark the shift from Coimbra's commercial quarter into the medieval uphill labyrinth, tracing the defensive walls toward the Tower of Almedina and pausing at the pink-housed slope that was once the city's first Jewish Quarter.