  In AdS/CFT, the entanglement wedge EW$(B)$ is the portion of the bulk
geometry that can be reconstructed from a boundary region $B$; in other words,
EW$(B)$ is the hologram of $B$. We extend this notion to arbitrary spacetimes.
Given any gravitating region $a$, we define a max- and a min-entanglement
wedge, $e_{\rm max}(a)$ and $e_{\rm min}(a)$, such that $e_{\rm min}(a)\supset
e_{\rm max}(a)\supset a$.
  Unlike their analogues in AdS/CFT, these two spacetime regions can differ
already at the classical level, when the generalized entropy is approximated by
the area. All information outside $a$ in $e_{\rm max}(a)$ can flow inwards
towards $a$, through quantum channels whose capacity is controlled by the areas
of intermediate homology surfaces. In contrast, all information outside $e_{\rm
min}(a)$ can flow outwards.
  The generalized entropies of appropriate entanglement wedges obey strong
subadditivity, suggesting that they represent the von Neumann entropies of
ordinary quantum systems. The entanglement wedges of suitably independent
regions satisfy a no-cloning relation. This suggests that it may be possible
for an observer in $a$ to summon information from spacelike related points in
$e_{\rm max}(a)$, using resources that transcend the semiclassical description
of $a$.
