Pannonian Basin in the context of "Vienna"

The Hungarian invasions of Europe (Hungarian: kalandozások, German: Ungarneinfälle) occurred in the 9th and 10th centuries, during the period of transition in the history of Europe of the Early Middle Ages, when the territory of the former Carolingian Empire was threatened by invasion by the Magyars (Hungarians) from the east, the Viking expansion from the north, and the Arabs from the south.

The Hungarians took possession of the Carpathian Basin (corresponding to the later Kingdom of Hungary) in a planned manner, with a long period of settlement between 862–895, and launched a number of campaigns both westward into former Francia and southward into the Byzantine Empire. The westward raids were stopped only with the Magyar defeat at the Battle of Lechfeld in 955, which led to the revival of the Holy Roman Empire in 962, producing a new political order in Western Europe. The raids into Byzantine territories continued throughout the 10th century, until the eventual Christianisation of the Magyars and the establishment of the Christian Kingdom of Hungary in 1000.

The Alps (/ælps/) are some of the highest and most extensive mountain ranges in Europe, stretching approximately 1,200 km (750 mi) across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia.

The Alpine arch extends from Nice on the western Mediterranean to Trieste on the Adriatic and Vienna at the beginning of the Pannonian Basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn.

Hungary is a landlocked country in Central Europe. Spanning much of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia and Slovenia to the southwest, and Austria to the west. Hungary lies within the drainage basin of the Danube River and is dominated by great lowland plains. It has a population of 9.6 million, consisting mostly of ethnic Hungarians (Magyars) and a significant Romani minority. Hungarian is the official language, and among the few in Europe outside the Indo-European family. Budapest is the country's capital and largest city, and the dominant cultural and economic centre.

Prior to the foundation of the Hungarian state, various peoples settled in the territory of present-day Hungary, including the Celts, Romans, Huns, Germanic peoples, Avars and Slavs. Hungarian statehood is traced to the Principality of Hungary, which was established in the late ninth century by Álmos and his son Árpád through the conquest of the Carpathian Basin. King Stephen I ascended the throne in 1000 and converted his realm to a Christian kingdom. The medieval Kingdom of Hungary was a European power, reaching its height in the Late Middle Ages.

Belgrade is the capital and largest city of Serbia. It is located at the confluence of the Sava and Danube rivers and at the crossroads of the Pannonian Plain and the Balkan Peninsula. According to the 2022 census, the population of Belgrade city proper stands at 1,197,114, its contiguous urban area has 1,298,661 inhabitants, while population of city's administrative area (which roughly corresponds to its metro area) totals 1,681,405 people. It is one of the major cities of Southeast Europe and the third-most populous city on the river Danube.

Belgrade is one of the oldest continuously inhabited cities in Europe and the world. One of the most important prehistoric cultures of Europe, the Vinča culture, evolved within the Belgrade area in the 6th millennium BC. In antiquity, Thraco-Dacians inhabited the region and, after 279 BC, Celts settled the city, naming it Singidūn. It was conquered by the Romans under the reign of Augustus and awarded Roman city rights in the mid-2nd century. It was settled by the Slavs in the 520s, and changed hands several times between the Byzantine Empire, the Frankish Empire, the Bulgarian Empire, and the Kingdom of Hungary before it became the seat of the Serbian king Stefan Dragutin in 1284. Belgrade served as capital of the Serbian Despotate during the reign of Stefan Lazarević, and then his successor Đurađ Branković returned it to the Hungarian king in 1427. Noon bells in support of the Hungarian army against the Ottoman Empire during the siege in 1456 have remained a widespread church tradition to this day. In 1521, Belgrade was conquered by the Ottomans and became the seat of the Sanjak of Smederevo. It frequently passed from Ottoman to Habsburg rule, which saw the destruction of most of the city during the Ottoman–Habsburg wars.

The Pannonian Avars (/ˈævɑːrz/ AV-arz) were an alliance of several groups of Eurasian nomads of various origins. The peoples were also known as the Obri (modern Russian: обры, Obry) in the chronicles of the Rus, the Abaroi or Varchonitai (Greek: Βαρχονῖται, romanized: Varchonitai), or Pseudo-Avars in Byzantine sources, and the Apar (Old Turkic: 𐰯𐰺) to the Göktürks. They established the Avar Khaganate, which spanned the Pannonian Basin and considerable areas of Central and Eastern Europe from the late-6th to the early-9th centuries.

The name "Pannonian Avars" (after Pannonia in the upper Danube basin where they eventually settled) is used to distinguish them from the Avars of the Caucasus, a separate people with whom the Pannonian Avars may or may not have had links. Although the name Avar first appeared in the mid-5th century, the Pannonian Avars entered the historical scene in the mid-6th century, on the Pontic–Caspian steppe as a people who wished to escape the rule of the Göktürks. They are probably best known for their invasions and destruction in the Avar–Byzantine wars from 568 to 626 and for their influence on the Slavic migrations to the Balkans.

Budapest is the capital and most populous city of Hungary. It is Hungary's primate city with 1.7 million inhabitants and its greater metro area has a population of about 3.3 million, representing one-third of the country's population and producing above 40% of the country's economic output. Budapest is the political, economic, and cultural center of the country, among the ten largest cities in the European Union and the second largest urban area in Central and Eastern Europe. Budapest stands on the River Danube and is strategically located at the center of the Pannonian Basin, lying on ancient trade routes linking the hills of Transdanubia with the Great Plain.

Budapest is a global city, consistently ranked among the 50 most important cities in the world, belongs to the narrow group of cities with a GDP over US$100 billion, named a global cultural capital as having high-quality human capital, and is among the 35 most liveable cities in the world. The city is home to over 30 universities with more than 150,000 students, most of them attending large public research universities that are highly ranked worldwide in their fields, such as Eötvös Loránd University in natural sciences, Budapest University of Technology in engineering and technology, MATE in life sciences, and Semmelweis University in medicine. Budapest also hosts various international organizations, including several UN agencies, the WHO Budapest Centre, IOM regional centre, the EU headquarters of EIT and CEPOL, as well as the first foreign office of China Investment Agency. Budapest opened the first underground transit line on the European continent in 1896, which is still in use as M1 Millennium Underground, and today the fixed-track metro and tram network forms the backbone of Budapest's public transport system and transports 2.2 million people daily, making it a significant urban transit system.

Banat (UK: /ˈbænɪt, ˈbɑːn-/ BAN-it, BAHN-, US: /bəˈnɑːt, bɑː-/ bə-NAHT, bah-; Romanian: Banat; Hungarian: Bánság; Serbian: Банат, romanized: Banat) is a geographical and historical region located in the Pannonian or Carpathian Basin that straddles Central and Eastern Europe. It is divided among three countries: the eastern part lies in western Romania (the counties of Timiș, Caraș-Severin, Arad south of the Mureș river, and the western part of Mehedinți); the western part of Banat is in northeastern Serbia (mostly included in Vojvodina, except for a small part included in the Belgrade Region); and a small northern part lies within southeastern Hungary (Csongrád-Csanád County).

The region's historical ethnic diversity was severely affected by the events of World War II. Today, Banat is mostly populated by ethnic Romanians, Serbs and Hungarians, but small populations of other ethnic groups also live in the region. Nearly all are citizens of either Serbia, Romania or Hungary.