  We review our recent work on four topics in strong-interaction physics from
the perspective of the gauge/gravity correspondence. In particular, we discuss
(i) the construction of the ``metric soft wall'' dual for holographic QCD which
reproduces the observed linear square-mass trajectories of radially and
orbitally excited (light-quark) hadrons, (ii) an extension of the metric soft
wall which encodes diquark correlations holographically and additionally leads
to an excellent description of the empirical nucleon excitation spectrum, (iii)
an AdS/QCD dual that emerges as a new solution of 5d Einstein-dilaton gravity
with a specifically derived potential and realizes the area law of the Wilson
loop and (approximately) linear meson trajectories dynamically, and finally
(iv) the calculation of glueball correlation functions and decay constants in
both the hard- and dilaton soft-wall gravity duals, as well as a quantitative
analysis of their QCD-relevant physics content.
