When you integrate RTL into a design, it helps to visualize the design inside the device. Graphically seeing how the blocks interconnect between themselves and the I/O pinout after synthesis helps you to understand your design.
To view the interconnect, generate a top level floorplan using Pblocks on upper levels of hierarchy.
Pblocks can be more than one hundred percent full during analysis, but not during implementation. Overfilling the Pblock makes them smaller on the device. This is a useful technique for getting an overview of the relative size of your design top-level blocks, and how they occupy the device.