CGAL (Computational Geometry Algorithms Library) is a large collection of geometric objects, data structures and algorithms. CGAL currently offers mostly functionalities for linear objects (points, segments, lines, triangles...). The first version of a kernel for circles and circular arcs in 2D was recently released in CGAL 3.2. We show in this paper a variety of techniques that we tested to improve the efficiency of the 2D circular kernel. These improvements are motivated by applications to VLSI design, and real VLSI industrial data are used to measure the impact of the techniques used to enhance this kernel. The improvements will be integrated in CGAL 3.3.