  The Ryu-Takayanagi prescription reduces the problem of calculating
entanglement entropy in CFTs to the determination of minimal surfaces in a dual
anti-de Sitter geometry. For 3D gravity theories and BTZ black holes, we
identify the minimal surfaces as special Lagrangian cycles calibrated by the
real part of the holomorphic one-form of a spacelike hypersurface. We show that
(generalised) calibrations provide a unified way to determine holographic
entanglement entropy from minimal surfaces, which is applicable to warped
AdS$_3$ geometries. We briefly discuss generalisations to higher dimensions.
