How to Make Model Railway Tunnels

Set up a piece of Styrofoam that is the appropriate thickness. If you use the large "O" or "G" scale, you will need a larger piece of Styrofoam than if you use the small "N" or "Z" scale.

Trace a semi-circle or other shape onto one end of the Styrofoam in a size that will be appropriate for your tunnel.

Cut into the Styrofoam using a hobby saw and burrow a passage through the Styrofoam to the other side. Because Styrofoam is beaded, you can make rough cuts to get a basic tunnel shape, then refine it in more detail with the saw or a hobby knife. Ensure the tunnel is tall and wide enough to allow each of your railroad cars to pass with enough clearance.

Cut the rest of the Styrofoam block to shape, if necessary. If you want the tunnel to appear as though it is cut through a hill or mountain, trim it into a smooth, curved shape with the hobby saw. If the tunnel should appear cut through a man-made structure, leave the Styrofoam block square on the sides and top.

Paint the inside of the tunnel black or dark gray with acrylic paint for added realism. Depending on how porous the Styrofoam is, you may have to paint more than one coat to achieve the desired level of darkness.

Decorate the Styrofoam tunnel with accents to make it appear more realistic. Hobby shops sell a variety of accents to use for this purpose, including sand, dirt, artificial shrubs, brick facades and trees. If you want the tunnel to appear built into a natural hill, cover the outside of the Styrofoam in hobby glue and sprinkle sand over it. Once the sand dries into place, glue accents such as shrubs and trees onto the Styrofoam.