In this demo paper, we introduce LatViz, a new tool which allows the construction, the display and the exploration of concept lattices. LatViz proposes some remarkable improvements over existing tools and introduces various new functionalities focusing on interaction with experts, such as visualization of pattern structures (for dealing with complex non-binary data), AOC-posets (the irre-ducible elements of the lattice), concept annotations, filtering based on various criteria and visualization of implications. This way the user can effectively perform interactive exploratory knowledge discovery as often needed in knowledge engineering, and especially in ontology engineering.