  We investigate some properties of n(\ge 4)-dimensional spacetimes having
symmetries corresponding to the isometries of an (n-2)-dimensional maximally
symmetric space in Lovelock gravity under the null or dominant energy
condition. The well-posedness of the generalized Misner-Sharp quasi-local mass
proposed in the past study is shown. Using this quasi-local mass, we clarify
the basic properties of the dynamical black holes defined by a future outer
trapping horizon under certain assumptions on the Lovelock coupling constants.
The C^2 vacuum solutions are classified into four types: (i)
Schwarzschild-Tangherlini-type solution; (ii) Nariai-type solution; (iii)
special degenerate vacuum solution; (iv) exceptional vacuum solution. The
conditions for the realization of the last two solutions are clarified. The
Schwarzschild-Tangherlini-type solution is studied in detail. We prove the
first law of black-hole thermodynamics and present the expressions for the heat
capacity and the free energy.
