Abstract: The panel (10) has a sandwich structure (11, 12, 13) with two outer stiff sheets (11, 12) defining a vacuum intermediate space between them and a sealing peripheral structure (14, 17, 18) disposed along the edges of the outer sheets in order to seal the vacuum intermediate space. The two outer sheets are spaced by an intermediate cellular body (13) located in the vacuum intermediate space. The cellular body (13) has cells (131) extending in a direction perpendicular to the outer sheets (11, 12). The cells (131) are intercommunicating with one another and have extended edges (132, 133) contacting the outer sheets (11, 12) for uniformly distributing thereon the stress caused by the external atmospheric pressure.