Nei primi decenni del XII secolo si realizzano in Sicilia numerosi edifici religiosi, le cui absidi seguono in genere i modelli bizantini, ma non mancano soluzioni originali. Tra le chiese basiliane del Val Demone si distingue quella dei Santi Pietro e Paolo a Casalvecchio Siculo (1117-1172), la cui abside centrale assume esternamente la forma di una torretta a pianta rettangolare, che include due nicchie pentagonali negli spazi di raccordo con la curva interna. Tutte e tre le absidi della chiesa di Sant\u2019Andrea a Piazza Armerina (ante 1148) presentano esternamente un profilo rettilineo e la massiccia struttura muraria ingloba la torre campanaria. Nella cappella palatina di Palermo, consacrata nel 1140, le tre conche sono unificate posteriormente da un volume poligonale, il cui riferimento pi\uf9 prossimo va ricercato nei modelli bizantini. L\u2019analisi delle strutture murarie evidenzia che tale geometria viene fissata fin dalla realizzazione della primitiva cappella del palazzo (la cosiddetta cripta), su cui poggia la chiesa superiore. Lo sperimentalismo planimetrico che si rileva in questi esempi, forse favorito dalle ridotte dimensioni degli edifici, verr\ue0 in seguito abbandonato in favore di soluzioni pi\uf9 consuete, privilegiando nelle absidi delle grandi cattedrali gli aspetti prettamente decorativi.Between the last decades of the 11th century and the beginning of the next, after Sicily's return to Christi- anity after the long period of Islamic rule, the island witnessed the almost simultaneous outburst of new constructions of religious buildings. It was a time of experimentation in spatial patterns and new building solutions that blended together the different cultures present on the island, namely the Byzantine, Islamic and Norman civilizations.
Due to their function and symbolic value, apses were always the focus of special attention, which in Nor- man churches was evident in the rich decoration of the facing walls, as opposed to the bare interior sur- faces, usually intended to accommodate mosaics or frescoes.
Alongside the "canonical" solution of the three curved volumes \u2013 corresponding to the ritual spaces of the bema, prothesis and diaconicon \u2013 adopted in the apses of the early cathedrals (Troina, Catania and Mazara del Vallo), various other alternatives were ex- perimented.
Among the Basilian churches, concentrated mainly in the mountainous areas of northeastern Sicily, the church of Santi Pietro e Paolo in Casalvecchio Siculo stands out for the originality of the apse. It is de- signed as an embattled tower with a rectangular plan built around the inner curve and the conch, forming two pentagonal niches at the base in the adjoining spaces. The Church was built around 1116, the year in which the Abbot Gerasimos received lands and other assets from Roger II, later King of Sicily, but it suffered serious damage as a result of the earthquake of 1169. It is no coincidence that two years later the
building was renovated at the expense of the cate- chumen Theosterictus under the direction of the pro- tomagister Girard the Frank, whose name seems to indicate that he came from France