By employing the new ultraspinning limit we construct novel classes of black
holes with non-compact event horizons and finite horizon area and study their
thermodynamics. Our ultraspinning limit can be understood as a simple
generating technique that consists of three steps: i) transforming the known
rotating AdS black hole solution to a special coordinate system that rotates
(in a given 2-plane) at infinity ii) boosting this rotation to the speed of
light iii) compactifying the corresponding azimuthal direction. In so doing we
qualitatively change the structure of the spacetime since it is no longer
possible to return to a frame that does not rotate at infinity. The obtained
black holes have non-compact horizons with topology of a sphere with two
punctures. The entropy of some of these exceeds the maximal bound implied by
the reverse isoperimetric inequality, such black holes are super-entropic.
