Abstract: The generation of subwavelength optical barriers on the scale of tens of nanometers, as conservative optical potentials for cold atoms, is discussed both theoretically and experimentally. In the proposed scheme they originate from nonadiabatic corrections to Born-Oppenheimer potentials for position-dependent “dark states” in atomic Λ configurations. The subwavelength optical barriers represent a “Kronig-Penney” potential, and I discuss the corresponding band structure including the effects of spontaneous emission and atom loss due to “bright” channels. Inclusion of an interparticle dipole-dipole interaction leads to formation of “domain wall molecules” and to unconventional Hubbard models with modulated in space interparticle interactions. As a brief discussion of potential applications, the subwavelength barrier can be used as a “splitter” to create a double-wire (or double-layer) with subwavelength spacing and, therefore, with substantially increased couplings as compared to ordinary optical lattices. As another application, specially designed subwavelength atomic internal-state spatial structures can be used for building an atomic scanning microscope with subwavelength resolution.