The town of Avesnes-sur-Helpe grew up in the 11th century on the top of a steep-sided hill above the river Helpe. The first fortifications were a strong donjon (large tower) and a circuit of stone walls surrounding the settlement.
These walls were expanded in the 13th century to take in a plateau to the west and the lower town, which had grown up next to the river. After a devastating siege by the French in 1477, the fortifications were reconstructed in the 1530s as artillery defences.
At this time the bastioned'system of artillery fortification was starting to spread outside Italy, where it had originated. The idea was that large angled bastions, with plenty of room for guns and good flanking capability, replaced the small round towers of the medieval era.
The Italian engineer Jacopo de Modena came to Avesnes to design the new fortifications, which were the first bastioned works in the Low Countries. Modena built a trace of six arrow-headed bastions'around the town, following the circuit of the medieval walls.
The bastions had casemates'for guns in their flanks and had a series of tunnels to access them, a common feature in the Italian School of Fortification. There were several irregularities in the trace, notably the bend in the centre of one the curtains and the indented flank by the south gate, the Porte de France.
One unusual characteristic of the fortress of Avesnes is that there is a big difference in height between the north and south parts of the town, which means that two bastions (the Bastion de la Reine and the Bastion St Jean are significantly higher than their neighbours.
However, any weakness due to poor flanking coverage from their northern neighbours was compensated for by the height of these two bastions. The height of both bastions meant that a breach in either of them would have been perhaps twice as high and steep as usual.
It is unclear whether this was a deliberate feature that was intended by Modena, or whether he simply designed the bastions according to the terrain, which dictated their height. It must be remembered that bastioned fortification was in its infancy in the 1530s and Italian engineers were still experimenting.
French forces were continually threatening the area in the 16th and early 17th centuries. They almost laid siege to Avesnes in 1552 but were prevented from doing so by bad weather. Avesnes was sold to Spain in 1556 and became a front line fortress defending the Spanish Netherlands against France.
In the first half of the 17th century the fortifications of Avesnes were reinforced. Five of the six arrow-headed bastions built in the 16th century were modified to form larger, straight flanked bastions. The Bastion de la Reine was not modified but left as an arrow-headed bastion.
The Bastion St Jean was enlarged to twice its original size and the top was rebuilt to be on two levels so that it could cover both the heights to the east and the river to the north. The Porte de Mons was rebuilt and a cavalier'was added to the Bastion de France.
However these new defences were not put to the test because Avesnes-sur-Helpe was ceded to France by the Treaty of the Pyrenees'in 1659. In 1661 the French engineer Vauban'visited the town to inspect the fortifications of the newly-acquired fortress.
Vauban planned improvements to the defences that were carried out over the following decade. He modified the outworks that had been built in front of the walls, realigning some demi-lunes'and doubling others.
A strong covered way'was added to protect the outer side of the ditch. Vauban also built cavaliers behind some of the bastions and a traverse on the low-lying Bastion de Ranty to protect it from being swept by an attacker's batteries on the high ground to the west.
Perhaps the most significant of Vauban's improvements was the construction of a sluice-bridge (called the Pont des Dames) across the river on the north side of the town. Protected by a demi-lune, these sluice gates allowed the garrison to control the water levels in the ditch on the north side of the town.
In the event of an attack the sluices could be closed to flood the area to the north of the town, preventing the besieger from attacking the fortress from the north. Finally, Vauban built powder magazines'and barracks for the garrison.
Avesnes was garrisoned throughout Louis XIV's'wars but did not see action. Perhaps the strength of the fortress, the relative unimportance of the town and the nearby fortress of Maubeuge were factors that discouraged invaders from targeting this section of the frontier.
During the 1830s the defences were restored and a new bastion was added in the centre of the long curtain wall in the south-east. This new bastion was smaller than the others, had straight flanks and was decked out with casemates where guns could be sited.
However, the revamped fortress did not last long. Bastioned fortifications were becoming obselete as artillery developed to be more powerful and have longer range. In 1867 the fortifications of Avesnes-sur-Helpe were declassified and in the 1870s some demolition was carried out in order to open up the town.
The demolition of the 1870s only removed sections of the fortifications, so a substantial amount has survived to this day. However, some of the remains have been neglected and are in poor condition or are inaccessible to the public.
The Pont des Dames can be accessed and the Porte de Mons is also in good condition, but it is difficult to get a view of the facade from the road. The Bastion Saint-Jean has recently been restored and can be visited. In the west, the Bastion de la Reine has also been restored and is accessible.
The best way to visit the fortifications is to start at the tourist information centre, not far from the Bastion Saint-Jean, to pick up a map showing the remains. Avesnes-sur-Helpe has a train station that is served by regular trains from Lille.