  Motivated by the need for further insight into the emergence of AdS bulk
spacetime from CFT degrees of freedom, we explore the behaviour of probes
represented by specific geometric quantities in the bulk. We focus on geodesics
and n-dimensional extremal surfaces in a general static asymptotically AdS
spacetime with spherical and planar symmetry, respectively. While our arguments
do not rely on the details of the metric, we illustrate some of our findings
explicitly in spacetimes of particular interest (specifically AdS,
Schwarzschild-AdS and extreme Reissner-Nordstrom-AdS). In case of geodesics, we
find that for a fixed spatial distance between the geodesic endpoints,
spacelike geodesics at constant time can reach deepest into the bulk. We also
present a simple argument for why, in the presence of a black hole, geodesics
cannot probe past the horizon whilst anchored on the AdS boundary at both ends.
The reach of an extremal n-dimensional surface anchored on a given region
depends on its dimensionality, the shape and size of the bounding region, as
well as the bulk metric. We argue that for a fixed extent or volume of the
boundary region, spherical regions give rise to the deepest reach of the
corresponding extremal surface. Moreover, for physically sensible spacetimes,
at fixed extent of the boundary region, higher-dimensional surfaces reach
deeper into the bulk. Finally, we show that in a static black hole spacetime,
no extremal surface (of any dimensionality, anchored on any region in the
boundary) can ever penetrate the horizon.
