Abstract. The adaptive landscape is an iconic metaphor in evolutionary biology. Any one evolving population of organisms explores such a landscape, whose highest peaks correspond to the best-adapted organisms. Finding such peaks can be extremely challenging if the landscape is rugged and harbors many suboptimal local peaks. Until recently, empirical evidence about adaptive landscape topography was completely lacking, and only theoretical analyses existed, which suggested that adaptive landscapes may indeed be rugged. We have used experimental data on transcription factor binding to thousands of different short DNA motifs to study not just one but more than 1000 landscapes associated with the evolution of gene regulation. We find that different landscapes contain different numbers of peaks that vary in their accessibility and in the number of genotypes they contain. Overall, however, these landscapes are highly navigable through single mutations, indicating that gene expression is readily fine-tuned via Darwinian evolution. Our observations suggest that landscape navigability may have contributed to the enormous success of transcriptional regulation as a source of evolutionary innovations.