De Conciliis became famous in 1965 for the realization of the "Mural of Peace", a monumental parietal work realized with the collaboration of Rocco Falciano, near the Church of San Francesco in Avellino. The fresco arouses lively controversy and captures the interest of the national and international press: behind the altar of a Catholic church is a fresco in which, around the figure of St. Francis, appear on one side images of war and destruction on the other, of peace and social justice. Alongside Pope John XXIII and the Avellinian bishops are John Kennedy, Mao Tse Tung, Cesare Pavese, Guido Dorso, Pier Paolo Pasolini and Fidel Castro. Criticized by the more traditionalist sectors of Catholicism. Previously an innovative crucifixion, realized for the Church of the Oblates in Avellino, had been canceled because it was considered unsuitable for a place of worship.
The artistic activity of de Conciliis continues in the following years with the construction of other impressive masonry with a social content: at the school of Cadelbosco (RE) he realizes "Effects of capitalism and the peace front", at the Study Center of Danilo Dolci in Trappeto (PA) "Clientelar system-mafia and non-violence", for the Municipality of Mantua a mural at the "Isabella d'Este" Magisterial Institute.
Among his works of public art are the Memorial of Portella della Ginestra, a land art intervention realized in 1979, in memory of the massacre of peasants made by the band of Salvatore Giuliano, and the Parco della Pace in Rome, with the construction of large sculptures dedicated to the Jewish, Islamic and Christian religions, together with an open-air theater and a "literary way" studded with stone-sculptures on which poetic verses are written, inspired by peace and brotherhood.
Currently his pictorial production is oriented on more intimate themes, with the representation of landscapes and still lifes.
Since 2005, the European Community and the Municipality of Fiano Romano have promoted the creation of a Studio-Museum in the medieval church of Santa Maria ad Pontem, where the master's works are collected.
Born in Avellino, he currently lives in Fiano Romano, after having stayed in Mexico and the United States.