Ballmann, W. Spaces of nonpositive curvature. (English) Zbl 1031.53069 Jahresber. Dtsch. Math.-Ver. 103, No. 2, 52-65 (2001). This is a brief survey of the theory of metric spaces of nonpositive curvature. Various rigidity results (mostly) due to Kleiner, Leeb, Brin, and the author are discussed in detail. Reviewer: Igor Belegradek (Pasadena) Cited in 19 Documents MSC: 53C24 Rigidity results 53-02 Research exposition (monographs, survey articles) pertaining to differential geometry Keywords:nonpositive curvature; flats; rigidity PDF BibTeX XML Cite \textit{W. Ballmann}, Jahresber. Dtsch. Math.-Ver. 103, No. 2, 52--65 (2001; Zbl 1031.53069)