We present the system dlvhex, a solver for HEX-programs, which are nonmonotonic logic programs admitting both higher-order atoms as well as external atoms. Higher-order features are widely acknowledged as being useful for various tasks, including meta-reasoning. Furthermore, the possibility to exchange knowledge with external sources in a fully declarative paradigm such as answer-set programming (ASP) becomes increasingly important, in particular in view of applications in the Semantic-Web area. Through external atoms, HEX-programs can deal with external knowledge and reasoners of various nature, such as RDF datasets or description-logics knowledge bases.