The article is devoted to one of the most exciting museum projects of the 1920th - Museum of the obsolescent cult, which existed in Petrograd in 1923-1927. The abolition of family and institutional chapels in the 1920th stimulated efforts to preserve its ornaments as a monument of history and culture of the two previous centuries. The work on the preservation of iconostases and artistic decoration of the closed churches began on the initiative of V. A. Tauber under the auspices of the Society of Old Petersburg. The ornaments were preserved, studied, restored and exhibited in a special building. The museum staff worked out a complex concept of a monument as a historically formed ensemble, which value depended on the preservation of historically established connections between its various elements. To create museum exposition the theatrical ideas of space organization were used. The article, based on documents of the archival fund of the Society of Old Petersburg, stored in the Central State Archive of Literature and Art of St. Petersburg, traces the history of the museum exhibition. Such prominent museum figures of the 1920th as M. V. Farmakovsky and N. E. Lansere took an active part in the development of its program. The museum was never open to the public. In 1927 due to financial difficulties and tensions within the Society of Old Petersburg, its collection was transferred to the State Museum Fund, which divided its items between several museums and research institutions of Leningrad. The change of names, under which the museum appeared in official documents, allows us to trace the various strategies used to "legitimize" church monuments - a dissonant heritage - in the discourse of Soviet Russia.