The present issue of 'La Rivista di Engramma' originates from a group of seminars focused on the bunker, in its manifold meanings. The title 'b???kë / bù?kër' -phonetic transcription of the two main pronunciations of the term- summarizes this multiplicity: in the first, the meanings of container and refuge coexist, in the second, the images and history of the war artefact are concentrated. The polarity of the adjectives through which it is possible to describe it - offensive / defensive, evident/hidden, inverted / everted, hypogeum / epigeal, punctual/continuous, decontextualized / part of the context, uprooted / rhizomatic, intimidating / protective, threatening / safe, functional / symbolic, form / absence of form, materiality / virtuality - together with the impossibility of identifying precise characteristics - perhaps the building material alone is what unites the bunkers - leads to consider it as a fleeting, fluid concept.