Whispering gallery to the walls, an effect that was discovered in the whispering gallery of St Paul's Cathedral in London. The extent to which the sound travels at St Paul's can also be judged by clapping in the gallery, which produces four echoes. Other historical examples are the Gol Gumbaz mausoleum in Bijapur and the Echo Wall of the Temple of Heaven in Beijing. A hemispherical enclosure will also guide whispering gallery waves. The waves carry the words so that others will be able to hear them from the opposite side of the gallery. The gallery may also be in the form
Speyer Cathedral an interior of monumental power, albeit stark and prismatic when compared with contemporary French buildings, but one which conveys an impression of Roman "gravitas", an impression singularly appropriate for a ruler with the political pretensions of Henry IV." In the course of these modifications the cathedral was equipped with an external dwarf gallery, an arcaded gallery recessed into the thickness of the walls, and which is a natural development of the blind arcade. Such blind arcades were used extensively as decorations, lining internal and external walls of many Romanesque churches. At the east end of Speyer Cathedral the dwarf gallery