The city of Frankfurt am Main started on a hill at a ford in the Main River. The city developed into a financial centre, nicknamed the smallest metropolis in the world.
Early history
Frankfurt is located in what was originally a swampy portion of the Main valley, a lowland criss-crossed by channels of the river. The oldest parts are therefore to be found on the higher portions of the valley, through which passed the Roman road from Mainz (Roman Moguntiacum) to Heddernheim (Roman Nida). The Odenwald and Spessart ranges surrounded the area, lending a defensive advantage, and placenames show that the lowlands on both sides of the river were originally wooded.
The oldest part of the Altstadt, the old city center, is the Cathedral Hill (Domhügel), upon an island created by arms of the Main. Only from the West could it be reached by foot without getting wet; this, together with its location at a ford, gave it significant military and economic advantages.
Stray archeological finds on the Domhügel go back to the Paleolithic, but the first proven settlement and land development date to the Roman era. It is assumed that the Romans settled on the hill in the last quarter of the 1st century CE; amongst other things, a Roman bath has been found, which may have belonged to a larger complex, possibly a fortress. Apparently the military occupation was abandoned during the 2nd century and replaced by a villa. Several farm buildings have also been excavated. A similar building complex was discovered at the modern Günthersburgpark in the Frankfurt-Bornheim portion of the city.
With the retreat of the Roman border to the west bank of the Rhine in 259/260, the Roman history of Frankfurt came to an end.
Early Middle Ages
The name Frankfurt first appears in writing in the year 793, but it seems to have already been a considerable city. In 794 a letter from the Emperor to the bishop of Toledo contained "in loco celebri, qui dicitur Franconofurd", which reads "that famous place, which is called Frankfurt."
It seems Cathedral Hill was already permanently settled in Merovingian times (possibly first by Romans). In 1992 excavations at the cathedral found the rich grave of a girl, that has been dated to the late Merovingian period of the 7th century.
Charlemagne built himself a royal court at "Franconovurd", the "ford of the Franks", and in the summer of 794 held a church council there, convened by the grace of God, authority of the pope, and command of Charlemagne (canon 1), and attended by the bishops of the Frankish kingdom, Italy and the province of Aquitania, and even by ecclesiastics from England. The council was summoned primarily for the condemnation of Adoptionism. According to the testimony of contemporaries two papal legates were present, Theophylact and Stephen, representing Pope Adrian I. After an allocution by Charlemagne, the bishops drew up two memorials against the Adoptionists, one containing arguments from patristic writings; the other arguments from Scripture. The first was the Libellus sacrosyllabus, written by Paulinus, Patriarch of Aquileia, in the name of the Italian bishops; the second was the Epistola Synodica, addressed to the bishops of Spain by those of the Empire, Gaul and Aquitania. In the first of its fifty-six canons the council condemned Adoptionism, and in the second repudiated the Second Council of Nicaea of 787, which, according to the faulty Latin translation of its Acts (see Caroline Books), seemed to decree that the same kind of worship should be paid to images as to the Blessed Trinity, though the Greek text clearly distinguishes between latreia and proskynesis; this constituted a condemnation of iconoclasm. The remaining fifty-four canons dealt with metropolitan jurisdiction, monastic discipline, superstition etc.
Louis the Pious, Charlemagne's son, selected Frankfurt as his seat, extended the palatinate, built a larger palace, and in 838 had the city encircled by defensive walls and ditches.
After the Treaty of Verdun (843), Frankfurt became to all intents and purposes the capital of East Francia and was named Principalis sedes regni orientalis (principal seat of the eastern realm). Kings and emperors frequently stayed in Frankfurt, and Imperial Diets and church councils were repeatedly held there. The establishment of religious monasteries and numerous endowments to the local church furthered the urban community. Also, as the Holy Roman Emperor had no permanent residence anymore, Frankfurt remained the center of imperial power and the principal city of Eastern Francia.