Use your keyboard keys to navigate.
The UP arrow key moves you up one level. So if you are in a particular project, let's say New York interior, you will move to all interiors. If you used the down arrow key before and the details of the project are visible, than this key consists of two stages. First it hides the project details, second it moves you up one level.
The DOWN arrow key show you the details of the project such as a description, name, authors, etc.
The LEFT and RIGHT arrow keys move you in a slideshow of project images.
You can use your mouse, just move to the edge of the image and click for the same effect.