Visigoth or Invisigoths?
From the beginning of the 6th century to the early years of the 8th, the Visigoths dominated Hispania (i.e. the Iberian Peninsula), but we would be hard put to find any substantial evidence of their presence. They are, as one observer has put it, the Invisigoths (See http://www.gadling.com/2010/12/31/the-visigoths-spains-forgotten-conquerors/).
Nevertheless, by the middle of the 7th century, they had imposed political, religious and legislative unity on Hispania, and ruled from their capital in Toledo, the centre of the Peninsula.
For the first time the Peninsula was governed wholly from within and not from outside, as had been the case under the Romans. How substantial these Visigothic contributions were for the future country of Spain (or Portugal) is open to debate. Some Spanish historians view these years as the birth of the nation, others reject even the idea that the Visigoths were Spaniards.
Despite some 200 years of domination, the Visigoths left no written record in their tongue, no towns of consequence, little in the way of buildings (some small rural churches), and little in the way of art (e.g. decorated pillars, votive crowns, bits of jewelry, figurative carvings). Even their one probable and significant contribution to Hispanic architecture, the horseshoe arch, is often attributed to the Moors.
Why such little immediately identifiable impact? Four factors perhaps account for this.
First, having already lived within the Roman sphere for a while before entering Hispania, the Visigoths admired the accomplishments of the Romans and considered themselves to be heirs to the Roman empire. Although conquerors of the Peninsula, they retained much of the Roman provincial administrative system and initially allowed the Hispano-Roman elite control of day-to-day matters.
They settled in Roman towns (Mérida is a good example), and gradually adopted or adapted Roman symbols of authority (the use of the crown, sceptre and throne, under Leovigild r. 569-86), Roman clothes (during Reccared I’s reign 586-601), Roman Catholicism (589, the year of Reccared’s conversion) and, of course, the language of Rome, Latin. They even used Latin on their gravestones.
Their own cultural identity, therefore, was stifled to all intents and purposes by the weight of a superior civilisation which they had “conquered.” We cannot talk, then, of a “Visigothisation” of the peninsula in the same way as we talk of its “Romanisation;” in fact, what we have is a “Romanisation” of the Visigoths”. “Visigothic Spain was,” as one writer pithily put it, “Roman Spain under changed management” (Fletcher 23).
Second, there was a large demographic disparity between invaders and residents of Hispania. Admittedly, there is no means of determining accurately neither the number of Visigoths who entered Hispania, nor the population of the peninsula when they arrived.
Figures for the Visigoths, for example, range from as low as 100,000 to 500.000; the estimated Hispano-Roman total varies from 4.000.000 to 6.000.000. What is consistent is that all investigators agree that there were far fewer Visigoths, which means that the task of imposing their values would have been formidable, especially in the relatively brief time of occupation (compared to the Romans and Muslims). And the reality is that Roman culture was much more deeply embedded in Hispania than it was, for example, in Galia (Gaul/France).
Third, although they eventually established their headquarters in Toledo under Athanagild/Atanagildo (r. 554-567) towards the middle of the 6th century –locating for the first time in Spanish history power in the centre of the Peninsula– the Visigoths were not an urban society in the Roman sense.
They were a nomadic people, tribal and warlike, which helps to explain why they did not go in for building towns. They were satisfied with settling in previously established towns, and only two of their own are recorded: Reccopolis and Victoriacum, both founded by King Leovigild (r. 569-86) in the second half of the 6th century. And of these only one, Victoriacum/Vitoria (or Olite according to some), still survives, although without Visigothic features; Reccopolis is just a bundle of ruins under excavation, near the village of Zorita de los Canes, just east of Madrid.

Barton, Simon A History of Spain Basingstoke, Hampshire & New York 2004.
Carr, Raymond ed. Spain: A History Oxford 2000
Collins, Roger Early Medieval Spain: Unity in Diversity, 400-1000 London 1983
Collins, Roger Visigothic Spain 409-711 Oxford 2004
Fletcher, Richard Moorish Spain London 1994
Phillips, William D, Jr. & Phillips Carla R A Concise History of Spain Cambridge 2010
Reilly, Bernard The Medieval Spains Cambridge 1993
Thompson, E.A. The Goths in Spain Oxford 1969
http://upload.wikimedia.org/wikipedia/commons/3/34/Recopolis_-_Vista_del_Yacimiento.jpg