Thin films of high-temperature superconducting YBCO are grown by pulsed laser deposition on single-crystalline substrates with artificial surface structures. Here, films can be grown that exhibit defect structures with can act as effective pinning sites for flux lines. Spatially-resolved magnetooptical investigations show a substantial increase of the critical current density. The figure depicts a typical surface topography of the substrate (a) and the current density in a YBCO film grown on top (b).