The Porta Nigra, referred to by locals as Porta, is a large Roman city gate in Trier, Germany. It is a UNESCO World Heritage Site.
The Porta Nigra viewed from the north.
Model of the Porta Nigra in Roman times (approx. 400 AD)
The Porta Nigra viewed from the town side (south).
Porta Nigra (aka Porta Martis) in 1670
A city gate is a gate which is, or was, set within a city wall. It is a type of fortified gateway.
Kent Gate is a city gate at the ramparts of Quebec.
Depiction of a guard checking a salesperson's papers at a city gate
Bab Agnaou is a city gate in Marrakesh.
Zhengyangmen is a city gate in Beijing.