Cleaning compositions in the form of a self-adhesive aqueous gel are provided. The aqueous gel may be a rigid, “hard” aqueous gel that resists deformation of its shape. The gel composition may desirably have a hardness of at least about 150 g and/or a gel melt temperature of about 50-90° C. The cleaning compositions may include a polyalkoxy nonionic surfactant, such as an alkoxylated alcohol and/or polymeric alkylene oxide block copolymer, a co-hardening agent, and water. Methods for treating a hard surface, such as a toilet bowl, using the cleaning compositions are also provided.