Start by creating a new file of header size. Create an ellipse using elliptical shape tool. Place as shown.

Double click the layer to open layer style window. Apply settings as shown.

Duplicate layer. Squeeze it vertically. Double click the layer to open layer style window. Apply Bevel & Emboss with following settings.

Similarly create more ellipses using ellipse tool. Apply same layer style that we used for first ellipse.

Using the pen tool create a shape behind small ellipses as shown. Fill with a darker shade of blue.

Create a few rectangles using rectangular shape tool. create rectangles with variable heights to give illusion of high rise buildings. Move these layers below all the layers in layer order in layer palette.

Insert a few cutouts of toons and place as shown.

Type navigation links over small ellipses.

Insert site logo and place on top.