This paper presents a fast and efficient focus+context technique, called DualView for navigating large graphs/hierarchies which are usually displayed in a high-density manner. The DualView includes two transformations: a browsing and a fisheye-like distortion. The browsing transformation is responsible for interactively exploring large hierarchies with a high-response rate and inexpensive computational cost. On the other hand, the fisheye-like viewer increases the degree of distortion of the image by increasing the original magnification function which is created by the browsing transformation. This dual enlargement enables users to see the detail of any interested area in a high-density visualization.