  We discuss models in which vacua other than our own can be directly observed
in the present universe. Models with density-dependent vacuum structure can
give rise to `non-lethal'-vacua: vacua with lower energy-density than our
vacuum, but only in regions with finite Standard Model densities. These models
provide an explicit example of a bubble which is confined to a finite region of
space and produces potentially detectable signatures, unlike standard Coleman
tunneling events where bubbles expand at the speed of light and are never
directly observable. We study the expansion and contraction of a confined
bubble created after a core-collapse supernova, focusing on energy deposition
that may be observable in the vicinity of a supernova remnant due to the
formation and evolution of a confined bubble.
