  We have investigated the behavior of three curvature invariants for
Schwarzschild, Reissner-Nordstr{\o}m, Kerr, and Kerr-Newman black holes. We
have also studied these invariants for a Schwarzschild-de Sitter space-time,
the $\gamma$ metric, and for a 2+1 charged dimensional black hole. The
invariants are
$I_{1}=R_{\alpha\beta\mu\nu;\lambda}R^{\alpha\beta\mu\nu;\lambda}$,
$I_{2}=R_{\mu\nu;\lambda} R^{\mu\nu;\lambda}$, and
$I_{3}=C_{\alpha\beta\mu\nu;\lambda}C^{\alpha\beta\mu\nu;\lambda}$. For all but
the Kerr-Newman case these invariants serve as either horizon or stationary
surface detectors. The Kerr-Newman case is more complicated. We show that
$I_{1}$ vanishs on the horizon in any space-time with a Schwarzschild like
metric.
