The cathedral of Santiago was designed with a floor-plan and series of special characteristics that come within a particular category of Romanesque architecture, commonly termed "Pilgrimage Art": large churches or basilicas, with barrel vaulting and through-stone arches in the central nave and groin vaults on the sides; churches which incorporate the retrochoir as a revolutionary architectural element. This structure permits large crowds to wander round the church without hindering the church services taking place in the central nave, it also makes it easier to visit the various relics located in the different chapels of the retrochoir. Together with these characteristics, there is also the triforium, with its galleries above the side naves, surrounding the entire cathedral. At least five churches can be included within this special group: San Martín de Tours, San Marcial de Limoges, San Sernin de Toulouse, Santa Fe de Conques and the most perfect of all, Santiago de Compostela.
Faced with the presence of such large numbers of pilgrims, and in order to mitigate the odour of the pious crowds, the Botafumeiro or incense burners were invented. The current Botafumeiro (which replaced the silver worked one taken by Napoleon in 1851 and which dated back to 1544) is now only a decorative item or tourist spectacle which can be seen in operation during solemn ceremonies and on all Sundays during Jubilee Year. The Botafumeiro is 1.5 metres high and weighs about 50 kilos. It is hung on a series of ropes and pulleys and seven men (the tiraboleiros) swing it from one side of the nave to the other. (In 1499 it flew out of the door of Las Platerías, before the eyes of princess Catherine of Aragon and was stopped by one of the tiboleiros jumping on top of it). It already existed in the 16th Century; as did other turibuli magni in the cathedrals of Zamora, Ourense and Tui.
From the book "Curiosidades del Camino de Santiago". by Juan Ramón Corpas Mauleon. Published by Edilesa