<p> Aldo Rossi (1931-1997) wrote the idea of “Città analoga”, before a the two tableaus titled Città analoga (Analogous City), one drawn in 1973 by Arduino Cantàfora and the other tableau collaged in 1976. On 22 May 1969, Rossi first wrote the idea of “Città analoga” in his diary, and Wittgenstein’s Propositions urged him to develop the idea from 1968 to 1970.</p><p> This study revealed that the birth of idea of “Città analoga” was impacted and developed with Wittgenstein’s Tractatus Logico-philosophicus, through The volumes of I quarderni azzurri (The Blue Notebook, shown as QA), the reprinted diary on which Rossi started writing from 19 June 1968.</p><p> It was argued that Rossi was attracted by Stonborough Villa designed by Wittgenstein before foundation of the idea of “Città analoga”. In the beginning of his diary, the whole pages of the volume 1 of QA written on 19 June 1968, he tried self-analysis of the terms that he had proposed as theory and recalled the similarity of design between Loos and Wittgenstein. Also, in the essay titled “Architettura per i musei”(1968), Rossi mentioned Wittgenstein’s villa and he noted the impact from Adolf Loos on Wittgenstein’s design. Then Rossi supposed that it would have been Schinkelian style if Hegel had designed architecture, as Wittgenstein designed Loosian architecture”. This assumption showed the analogical way of his theory. From 1968 to 1969, in the last page of volume 2 of QA, Rossi noted Proposition 6.54 in Tractatus Logico- philosophicus, “a ladder that must be thrown away after one has climbed it”. It was connected the idea of “Città analoga” shown on 22th May 1969. The birth of “Città analoga” was assumed in that day, for the He underlined “Città analoga” and reflected the idea that would have expected the collage in 1976 in that page. On 2 December 1969, he connected the idea of “Città analoga” to the fragments of urban landscape of De Chirico and Mario Sironi, and cited Manifeste du surréalisme written André Breton. This meant that Rossi discovered the idea of “Città analoga” and threw the ladder of logic inherited from Wittgenstein. On 31 March 1970, in the volume 4 of QA, Rossi associated the idea of “Città analoga” with two proportions of Tractatus Logico-philosophicus. There, Rossi cited the Proposition 6.522 ("There is indeed the inexpressible. This shows itself; it is the mystical") and that of 6.4 ("All propositions are of equal value"). These citations meant that fragments of image for architectural design included “the mystery” and that the fragments had “equal value” and constituted logical process in the idea of “Città analoga”. For the conclusion, Wittgenstein’s architecture and theory encouraged Rossi to develop the idea of “Città analoga” from June 1968 to March 1970. In other words, Rossi counted the idea as constitution of fragment of scene. The collage gathered with pieces of scene like autonomous proportions enabled the architect to brand the process of thinking in “Città analoga”.</p>