---
title: "Tower XII and the City Walls - Pompeii Online"
description: "The ancient city of Pompeii: Information on visiting hours, tickets, guides, online tickets, tourist itineraries, news and much more."
url: "https://www.pompeionline.net/en/buildings-and-places/suburban-area/tower-xii-city-walls"
date: "2026-09-15T08:47:24+00:00"
language: "en-GB"
---

#  Tower XII and the City Walls

**Tower XII** formed part of Pompeii’s defensive system and stands along the north-western sector of the city walls, between **Tower XI, known as the Tower of Mercury, and the Herculaneum Gate**. The structure lies at the northern end of the Vicolo di Modesto and defended one of the stretches of fortification overlooking the territory north of the city.

The tower belonged to the extensive fortification system strengthened in the early **1st century BC**, shortly before Pompeii was besieged by the troops of Lucius Cornelius Sulla in 89 BC. Archaeological investigations have associated this phase with the construction of twelve towers in ***opus incertum***, placed mainly along the northern and eastern sectors of the walls, where the terrain offered less natural protection.

**Tower XII** is of the same architectural type as Towers X and XI. It originally rose through **three levels**, connected by an internal system of stairways. The entrance on the city side led to two flights: one descended to the lower chamber, while the other gave access to the upper level.

The lower floor contained a large **barrel-vaulted chamber**. From the rear of this room, a passage led to a small **postern** opening on the outer side of the fortifications. At the upper levels, further doorways connected the tower with the wall walk, allowing defenders to move quickly along the circuit.

The walls were pierced by **arrow slits**, positioned to command the ground outside and the tower’s access points. The distinctive arrangement of Towers X, XI and XII reveals a unified design, conceived to combine defence from the tower’s different levels with defence along the curtain walls.

The present state of preservation of Tower XII is very different, however, from its appearance when the defensive system was still fully operational. The earthquakes that struck Pompeii during the **1st century AD** caused serious damage to both Tower XII and nearby Tower XI. The upper sections collapsed, and Tower XII entirely lost the **façade facing outside the city**.

After this damage, some of the original passageways were closed with relatively simple masonry. These alterations show that the structure was not fully rebuilt in its original military form, but was at least partly made safe at a time when the fortifications had long since lost their strategic importance.

The walls had begun to lose their military role much earlier. Following the Roman conquest and the foundation of the colony in **80 BC**, Pompeii no longer needed to maintain a defensive system comparable with that of the earlier Samnite city. The towers continued to mark the urban boundary, but some passages were closed and various structures were gradually adapted or abandoned.

Tower XII also provides direct evidence of the relationship between the later towers in ***opus incertum*** and the earlier phases of the city walls. The adjacent stretches preserve imposing curtain walls of large squared blocks, belonging to the oldest fortifications and later incorporated and altered during the many interventions that affected the defensive circuit.

The blocks of the walls near the tower also bear numerous **marks cut by ancient stonemasons**, connected with the working and setting of the stone elements. These traces are valuable evidence for the techniques used to build the fortifications and for the organisation of the craftsmen engaged in the work.

Proceeding west from Tower XII, the city walls continue towards the **Herculaneum Gate**. This stretch preserves some of the most imposing ashlar masonry in the entire Pompeian circuit. To the east, the fortifications reach **Tower XI, or the Tower of Mercury**, forming one of the clearest surviving sectors of the northern walls.

The modern excavation of Tower XII is closely connected with investigations of the northern walls. Between the late 19th and the early 20th century, this sector was gradually cleared of the deposits covering it; major work was also carried out during the clearance of the stretch of city wall between **the Vesuvius Gate and the Herculaneum Gate**, documented in the 1940s.

The structure visible today preserves chiefly the lower level, the broad opening of the vault, and portions of the side and rear walls. Despite the loss of the outer façade and the upper storeys, the surviving arrangement still makes it possible to understand how the tower functioned and how it connected with the wall walk.

**Tower XII and the city walls** therefore provide particularly significant evidence for the development of Pompeii’s fortifications. The vaulted chamber, the system of stairways and passages, the earlier curtain walls and, above all, the damage and closures introduced during the city’s final decades trace the transformation of a structure conceived for military defence into an element absorbed into the urban landscape of Roman Pompeii.

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