The new building for the central station Hauptbahnhof was opened in May 2006 and together with Südkreuz (southern cross) and Ostbahnhof (eastern station) - plus minor Gesundbrunnen in the north and Spandau in the west - form the backbone of all connections. All are connected to either S- or U-Bahn (and in the future, both). All trains travel through central station and a second major hub (depending on the destination you travel to or arrive from). Trains in the regional area (Berlin and Brandenburg) mostly use these stations. Regional trains stop at several stations within Berlin.
In 800, the Frankish king Charlemagne was crowned emperor and founded the Carolingian Empire , which was later divided in 843 among his heirs.  Following the break up of the Frankish Realm, for 900 years, the history of Germany was intertwined with the history of the Holy Roman Empire ,  which subsequently emerged from the eastern portion of Charlemagne's original empire. The territory initially known as East Francia stretched from the Rhine in the west to the Elbe River in the east and from the North Sea to the Alps .  The Ottonian rulers (919–1024) consolidated several major duchies and the German king Otto I was crowned Holy Roman Emperor of these regions in 962. In 996 Gregory V became the first German Pope, appointed by his cousin Otto III , whom he shortly after crowned Holy Roman Emperor. The Holy Roman Empire absorbed northern Italy and Burgundy under the reign of the Salian emperors (1024–1125), although the emperors lost power through the Investiture Controversy .