Fortress City Mainz Germany

At the confluence of Main and Rhine a Roman military basis to protect the limes and conquer Germania was built already in 13 before Christ. Mogontiacum (Latin for Mainz) became a vibrant Roman legion city with war port, Rhine bridge and Castellum for around 500 years. The Drususstein, the Roman theatre and also the Roman Germanic museum at the residence castle show this important epoch.

From the 3rd century a Roman city wall was built which was expanded to a medieval city fortification from the 9th century In 1163 it was taken down again by imperial penalty – because the Mainz citizens assassinated the bishop Arnold von Seelenhofen during a riot. From the 13th century, when things have calmed down, it was rebuilt and expanded up to 5 meters high. City gates and towers were added.

From 1620 Mainz became a Baroque fortification for the electors. The Schweickhardsburg was built on the Jakobsberg and gun emplacements and entrenchments were built. From 1655 elector Johann Philipp von Schönborn had the citadel built instead of the Schweickhardsburg and had the bastion ring extended. Between 1792 and 1814 Mainz was mostly a French border and offensive fortification with many besiegement.

In 1793 Johann Wolfgang Goethe as eyewitness described the besiegement of Mainz by Prussia, Austria, Saxony, Bavaria and Hesse during which the French surrendered after 2 months. Only in 1797 they returned and stayed until 1814. During this time Napoleon came to Mainz 9 times.

The After it was given to the Germans in 1814 it was expanded to a fortification of the German Federation until 1866. In connection with the other federal fortifications Ulm, Rastatt, Landau and Luxembourg a new attack by France was to be avoided. Due to an explosion of the Mainz powder magazine the gable stone was thrown around 500m into the old city and lies there until today.

From 1870 to 1918 the imperial fortress Mainz was developed with a larger fortification ring of more than 300 bunkers and positions including fortress train for supplies. The citadel was used as a war prisoner camp. The Treaty of Versailles finally sealed the end of Mainz as a fortified city and slightings of large areas began which concentrated especially on the bunker ring.

During World War II a war prisoner camp was built in the citadel. The underground fortification halls were used as bomb shelters. From 1945-1955 the French occupation force moved into the citadel and had destroyed building rebuilt.

Learn more about the history.

Many architectural highlights from the long history of fortification architecture are located in Mainz. Famous architects, as Johann Maximilian von Welsch, were part of this development. The citadel is well-worth seeing with its classic ground plan, four bastions and the gate house. Also the Rhine gates, caponiers and Gau gate are impressive.

The commander building on the citadel

Towards the city the commander building built over the west entrance rises up. It was built in 1696 under the Mainz elector Lothar Franz von Schönborn and served the current fortress commander as business location. The building consists of three wings and as many storeys. A large terrace is located between the wings. The red and white building is crowned with a “Mansard roof” – the first ever in Mainz. In 1833 a additional storey was built and the Mansard roof destroyed, but the French occupation had it rebuilt to its original scope after World War II.

Under the commander building is the gate facility built around 1660. Today most visitors reach the citadel through there. It used to be directly under the wall and was integrated in to the commander building during its construction. The Baroque gate looks toward the city and was built by Italian architect Antonio Petrini. His style were sticking out sandstones which were to support the character of the fortification and a scary “stone grimace”. Above in the tympanum two lions hold the coat of arms for elector Johann Philipp von Schönborn, the architect of this citadel. It shows the double Mainz wheel, the rake of dukedom Franconia and the flag of diocese Würzburg in four fields. Johann Philipp von Schönborn reigned those areas around 1660. The middle shows the family coat of arms of Johann Philipp von Schönborn as the heart shield: A lion walking over the Franconian rake. On a closer look the Schönborn lion has two tails. Until today it is not clear why.

Guide rollers on the right and the left of the archway remember of the former existing drawbridge. If a visitor enters the gate way a weird kink is catching the eye: it made it possible to fire frontally on a entering enemy and not only from the side as it would be the case on a straight way. A portcullis and a hole, from which garbage could be poured over the intruder, served as additional protection. But they lost their function when the commander building was built above the gate facility.

In the gate way are two stones with inscriptions. Both seem to be put in this place subsequently. The smaller stone names the constructor and the first constable of the citadel: Adolph von Waldenburg. The biggest stone shows the coat of arms of elector Georg Friedrich v. Greiffenklau zu Vollrads (right) – under whom the Schweickhardtsburg was finished in 1629 – and the coat of arms of the Mainz cathedral chapter (left).

Gau gate

The Gau gateway was besides the Münster gate the most important connection to the outside from medieval Mainz. The word “Gau“ originates from Middle High German and means „country” or “region”. The medieval Gau gateway actually consisted of three gates: the inner gate, the middle gate and the outer Gau gate. While the bridge tower stood above the middle gateway, the outer Gau gateway was secured by the Martin tower. Between the inner and the outer gateway is a distance of around 150m. Already in 1462 during the Stift feud the Gau gate became sadly famous: on this seemingly most secured spot of the medieval city fortifcations the troops of Adolf II von Nassau achieved the breakthrough. This not only ended the feud between him and Dieter von Isenburg, but also the 200 years history of a “free” Mainz.

During the Swedish times (1631-36) the Gau gate was surrounded by earth work. When building the bastion fortification ring around Mainz in the 1650s under elector Johann Philipp von Schönborn, a stonewalled cross wall was built with a passage instead of the Gau gates. This passage had a facade to the city and the country. The preserved outer Gau facase shows Roman Baroque characteristics. The gable of the gate shows the holy Martin with two beggars (a copy since 2002). In front of the gate was a stone bridge which reached over the fortress trench.

The inner and middle Gau gateway had to give way to the new Gau gate. The outer Gau gate with Martin tower remained within the bastion Martin, which is connected to the Gau gate in the north – until a neighbours powder magazine exploded in the afternoon of the 18th November 1857.

In 1896 the Gau gate and the fortress wall were grounded and the trench in front filled up. Only strong protests by Mainz citizens saved the Gaugate from destruction. But it took almost hundred years until it came back to its original location. Only in 1998 the façade of the Gau gate was placed near its original location – the entrance of Gau alley.

The green elements of the citadel Mainz is the richest in species in the developed are in Mainz. It is especially important regarding ecology: The area of the citadel has around 450 animals and plants, of which 66 kinds are on the red list of the Federal Republic of Germany and the state Rhineland-Palatinate. As the green lung the protected landscape part provides fresh air for the inner city.

The flora and fauna which developed over centuries in parts of the citadel is of a priceless value today: 447 animal and plant species, among them birds, bats and wild bees. 66 species are even on the red list, for example long-eared bat, long horn bee, pygmy stag beetle, yews and flaked mullein. Especially bird life shows a remarkable number of species and high brood density, which traces back to the natural wood and the alleged undergrowth. 44 bird species were watched, for example the blackcap, lesser whitethroat, song thrush, pied flycatcher, goldfinch, linnet, robin redbreast, spotted woodpecker and green woodpecker. Birds especially like to nestle in the brambles, which offers protection of enemies and are densely branched. The hollow stems alos serve as an all-year habitat for wild bees.

The walls of the citadel are even of federal meaning. 170 species of aculeatas were found like digger wasps and wild bees. Those depend on the little hollow parts of the walls and nestle places (ovipositor). Insects living in the wall and plants in the walls serve as nutrition. Those herbaceous plants as the bell flower don’t damage the walls. Very special is also the age of the citadel walls, that means there are habitats undisturbed for centuries, which contain besided the species diversity also ancient populations and genetic reservoirs of the species.

The walls of the citadel belong to the country-wide most important moss biotopes. Ivy protects the walls in many places from weathering. It is evergreen and protects the animals all-year. Other than other plants it blooms late (from September) and fruits earlier and is important during this otherwise poor in nutrition times. The ivy colletes is specialised on ivy pollen to raise its brood.

In the underground ways and casemates, bates as the long-eared bat and the Daubenton’s bat can be found. Other species come together in the evening to hunt. They fly to the plants on the walls and hunt insects that are attracted by the flowers.

For its inhabitants the green and the walls of the citadel are unreplaceable habitats that are not available anymore anywhere close by. When damaged, whole biotic communities can break down. More over the green elements of the citadel serve as the green lung of the city. Structurally this is closed off from fresh air lanes of the surroundings. The citadel green filters the air, cools down and humifies the dry and hot city climate up to the housing estates. In summer the fresh air can be felt in the citadel trench. The high value of the citadel green led to designation of the trench and parts of the walls as protected landscape part (GLB) according to §29 of the federal nature protection law.

Pilot project "ecologial wall restauration citadel Mainz" and overall concept citadel

Principally a connection of nature protection and monument protection is possible. The citadel area offers enough space for it with an area of around 10 hectare and a wall length of around 2 km. There can be areas which concentrate on nature protection (for example the citadel trench), monument protection (for example commander building and run-up) and combining nature and monument protection (for example bellflowers on the wall, green are with view of the dome).

Where the walls need to be restored, the nature can be renewed carefully. As part of the project “ecological wall restauration citadel Mainz” (2006-2009), which is financed by the German federal foundation for the environment, a guideline was developed in cooperation of official and voluntary representatives of nature and monument protection, which regards aspects of monument care and ecology as the breeding period of birds and the preservation of harmless vegetation.