Fortifications

Fortified locations, military constructions, or buildings, have been built from antiquity all the way to the present. At many archaeological sites and in some old towns they are the dominant structures.

Understand
The earliest fortifications, were most likely additions to an already defensible positions afforded by natural topography. Types of fortifications are varied, with new developments continuing all the way to the present. The Romans were also prolific builders of military infrastructure (such as Hadrian's Wall). In Asia, the Great Wall (built to protect a unified China) was commenced in 221 BC.

A hill fort is a natural elevation used as fortress, with less steep sections strengthened by walls, stockades or other structures. They were built by peoples in prehistoric and ancient Europe, such as the Celts and the Old Norse.

A stockade is an enclosure of vertical logs. It is easier to build than a masonry fort, and has been used around the world against lightly armed enemies at least since the Roman Empire; especially in colonial settlements such as the American West.

A city wall was common for ancient and medieval cities; not just for defense, but also for toll collection. As walls became obsolete, many of them were torn down to scavenge the stone, or to make room for new buildings or railroads. While few intact city walls remain, the perimeter is still visible in many cities, as a sharp border between medieval and early modern architecture. The wall of Nanjing is one well-preserved example.

A citadel is a fortification complex which protects a city; usually with many military or civilian buildings on the inside.

Castles are fortified residences, usually of the local lord. They were mainly built in Europe, the Middle East and Japan from the 10th century AD, before development of cannons rendered them less defensible.

The bastion fort, also known as star fort, was prevalent in early modern Europe and European colonies from the 15th to 19th centuries, as a platform for cannons, and defense against enemy cannons and firearms.

In the 19th century, cities became larger and cannons became stronger, and bastion forts were replaced by polygonal forts which were partially underground, usually clustered along strategic defense lines outside cities.

The development of high-explosives toward the end of the 19th century, and of aerial warfare and reconnaissance in the early 20th century, saw a shift from surface fortifications, to hardened structures and bunkers below the ground. Many of the military fortifications which have been in use since World War II are also underground works, serving as different kinds of bunkers, command centres and bomb shelters.

Military sites
Not all fortifcations are necessarily open to the traveller (even on an organized tour). It should be especially noted that military facilities (even if seemingly abandoned or out of use) often remain highly sensitive sites, with restrictions for photography, drone flight, and other kinds of intrusion. An unexpected or unannounced visit could at best lead to a lengthy interrogation, with considerably worse outcomes depending ultimately on the mood of the personnel you encounter. You should make formal contact in writing with the relevant military authorities as soon as you have firm travel plans. Do not be disappointed if a planned or agreed visit has to be cancelled or curtailed for operational and security reasons. Or if you are denied access without any reason at all being provided.

Europe
While the Roman Empire had many river borders (not because rivers were uncrossable, but because patrolling them by boat was easier than patrolling land borders), in places where no river was available, they built walls and fortresses, some of which remained distinctly visible for centuries, with the Germanic Limes and Hadrian's Wall in Northern England perhaps the most notable. However, it was the Middle Ages with its countless mid sized and tiny polities and warfare with heavy focus on relatively small heavy cavalry units and siege warfare that gave rise to many European fortifications still in existence to this day.

Baltic states
The Baltic States have been subjects of the Teutonic Order, the Swedish Empire, the Russian Empire and the Soviet Union. Estonia in particular has plenty of coastal forts from different ages.



Finland


While Finland used not to have the wealth for massive fortifications, there are indeed some. Iron Age hill forts are relatively common, there are castles, not protecting lords but the king's representatives and strategic locations, built under the Swedish Empire, such as the great Sveaborg/Suomenlinna fortress from the 18th century, and later the Russian Empire, such as the equally grand Bomarsund on Åland (destroyed by the English and French in the Crimean War) and parts of the "Peter the Great" chain of fortifications of the early 20th century. Parts of the Salpa Line from World War II, along the Russian border, also remain, often in off-path locations such as Tankavaara, Savukoski, Virolahti and Miehikkälä, but also near Joensuu. Several 20th-century coastal artillery forts have been opened for visitors.



France
In part due to a distinct manpower disadvantage caused by lower French birth rates, France built fortifications for both World War II in Europe and World War I. Germany tried to go around the bulk of those in both wars by violating the neutrality of Belgium. While the French plan was partially successful in World War I, the "Maginot Line" as it was called was not able to stop or even delay the rapid advance of German tanks in World War II. While some argue that the purpose always was to force the German army to once more violate Belgian neutrality and invade through the Ardennes (a heavily wooded, hilly terrain, then deemed unsuitable for major offense) the fact of the matter is that France capitulated in a matter of weeks in 1940.
 * Fortifications of Vauban

Germany
The English term castle has two words with different nuances of meaning in German. A Burg (from which the word "burgher" is derived, a person who can expect protection in a Burg) is mainly a fortification, where any purpose as a residence is secondary, whereas a Schloss is largely a palace; a representative building with little or no military value. However, many a Schloss is made to look like a Burg and even originally military buildings may have taken on non-military purposes later on. Festung is a generic German word for a fortress.





Romania
Cule, the formidable fortifications that dot the landscape of south-western Romania, particularly Oltenia, are a testament to the rich history and strategic importance of this region. These resilient structures, characterized by their distinctive architectural style, serve as guardians of the land, not only in Romania but also across various Balkan countries where their influence can be found. Embedded with tales of resistance and resilience, these cule stand as enduring symbols of the region's cultural heritage and the indomitable spirit of its people.

Russia
Russian cities are known for having a distinctive type of fortress known as a kremlin, of which the one in Moscow is undoubtedly the most famous, and remains the seat of the Russian government to this day. Usually, you can except to see a number of churches within the walls of a kremlin.

Sweden
Sweden has several ancient hill forts (fornborg). Sweden had rather few castles in the Middle Ages; many castles and fortresses were built for the 17th- to 18th-century Swedish Empire. While Sweden has not been at war since 1814, the country has extensive underground bomb shelters built for the World Wars and the Cold War.
 * Stockholm's northern defenses are a long line of land and coastal structures used from the 17th to the 20th centuries.
 * Boden fortress: A fortification system from the 19th century
 * Stockholm's northern defenses are a long line of land and coastal structures used from the 17th to the 20th centuries.
 * Boden fortress: A fortification system from the 19th century

Switzerland
While the Swiss last went to war in 1848 in a civil war mostly between Catholic conservatives and Reformed liberals and Switzerland was last invaded by a foreign power in the Napoleonic Wars, the Swiss had an elaborate and costly defense scheme in place for World War II in case Germany (or any other power) ever violated Swiss neutrality. This "national redoubt" was for a time credited with making invasion seem so costly as to make Germany reconsider; however, these days many historians point out that the Nazis had little to gain from invading Switzerland and neutral Swiss banks were an important factor for the German wartime economy.

Middle East
The Middle East is the cradle of organized warfare with standing armies distinct from the general population and thus also saw some of the earliest sieges we know of. However, many of them are archeological sites or buried between several layers of newer construction. The Trojan War took place in what is now Anatolia and is said to have involved a ten year siege with projection of power across the Aegean Sea over three millennia ago. During the Crusades, "Crusader States" arose in the Levant, establishing a tiny (largely immigrated) Catholic elite in largely Muslim, Jewish or non-Catholic Christian regions and as such the rulers built impressive (and in some cases still extant) fortresses to defend their hard won territories against the inevitable Muslim counterattack.

Turkey
Due to its position along the major routes of the Old World, trampled as many invaders as traders, Turkey is very rich in fortifications, ancient and modern alike. For a start, the Theodosian Walls of Constantinople, impregnable and unbreached until the advent of heavy artillery, are arguably the world's most iconic historic fortification, most of it still standing despite the battle damage from the 1453 Ottoman siege. The banks of the Turkish straits are lined with many other impressive fortresses, often with commanding views of their surroundings—see the Istanbul and Çanakkale articles for full details.

Many towns along the Aegean and Black Sea coasts feature fortresses that started life as trading posts of the Genoese, who controlled trade in the medieval Mediterranean. The lush hillsides and valleys of Eastern Karadeniz, in the far northeast, are dotted by castles that are often likened to those found in fairy tales, while Çukurova (Cilician Plains) in the south of the country is home to a relatively large number of Crusader-era fortresses. The isolated Mediterranean coast to the west is the site of a couple castles that are often considered the most scenic in the country. Further west, Bodrum, Antalya, and Alanya have some of Turkey's most famous and well-visited castles.

China
The Great Wall of China is a series of walls, expanded throughout the long history of Imperial China.