xTerior: Exterior calculus in Mathematica. xTerior is a package for exterior calculus running under Mathematica. Some of its most notable points are: Efficient representation and handling of tensor valued differential forms. Implementation of the exterior derivative, the exterior covariant derivative, the co-differential and other standard derivations used in exterior calculus such as the inner contraction and the Lie derivative applied to differential forms. Possibility of computing variational derivatives of top rank forms. Full integration of coordinate charts with the aid of the xAct package xCoba. Implementation of the standard Cartan structure equations in generic co-bases and explicit coordinate representations.