Model railway construction is a hobby that people of all ages can enjoy. A model railway can be as simple as a circular track laid out on a piece of plywood or as complicated as a realistic-looking diorama that includes bridges and tunnels. You can construct model railway tunnels with ease and finish them with details that will add realism.
Set up a piece of styrofoam that is the appropriate thickness. If you use the larger scale railway tracks, you will need a larger piece of styrofoam than if you use the smaller gauge railway layout.
Trace a semi-circle or other shape on to 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 model trains 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 grey 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 and modelling 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 on to the styrofoam.
If you cannot buy a sheet of styrofoam thick enough to cut a tunnel through, buy multiple sheets of styrofoam and glue them together.