two pairs of tall towers which frame the nave at the western end and the chancel to the east, and form a sculptural mass with the dome at each end, creating an "equilibrium between the eastern and western blocks". The majority of its features are still the same exterior but the interior has undergone many renovations supporting the foundation but changing the interior greatly. The exterior appearance of the cathedral is unified by the regularity of the size of its openings. Speyer has the earliest example in Germany of a colonnaded dwarf gallery that goes around the entire building, just below the roofline. The same type of gallery also adorns the eastern and western domes. The openings in the gallery match the size of the paired windows in the towers. The domes are both octagonal, the roof of the eastern one being slightly ovoid. The towers are surmounted by "Rhenish helm" spires. The nave, towers and domes are all roofed with copper, which has weathered to pale green, in contrast to the pinkish red of the building stone, and the polychrome of the Westwerk. Internally, the nave is of two open stages with simple semi-circular Romanesque openings. The arcade has piers of a simple form, each with a wide attached shaft, the alternate shafts carrying a stone arch of the high vault. The square bays thus formed are groin vaulted and plastered. Although most of the plasterwork of the 19th century has been removed from wall surfaces, the wide expanse of masonry between the arcade and the clerestory contains a series of colourful murals depicting the Life of the Virgin. The cathedral has recently undergone fundamental restorations, which cost around 26 million Euros. In addition the frescos by Johann Schraudolph, which were removed in the 1950s, were restored and are now displayed in the "Kaisersaal" of the cathedral. World Heritage Site In April 1981, Speyer Cathedral was added to the UNESCO World Heritage List of culturally important sites. The International Council on Monuments and Sites (ICOMOS) justified the inclusion: "The cathedral of Speyer, with those of Worms and Mayence (Mainz), is a major monument of Romanesque art in the German Empire. It is, by virtue of its proportions, the largest and the most important; by virtue of the history to which it is linked – the Salic emperors made it their place of burial." ICOMOS also cites the building as