Step 1.
Fertile bridge land. � 1. First, pick a nice flat area in your city. If you want to build a land bridge in a particular area, use the Level Terrain tool from the Landscape menu to flatten the area. Then, make a slender lake with the Landscape menu's Water Dropper. The amount of water you place will depend on how long you want your land bridge to be.

Step 2.
Lowered terrain in front of the water. � 2. If you try to build the bridge over this water, you will probably get a warning that buildings obstruct the span. To get around this, you'll want to lower the terrain in front of the starting edge of the water you created with the Lower Terrain tool from the Landscape menu. Lower the terrain there a few clicks.

Step 3.
Dragging road over our rig to create a bridge. � 3. Now, starting a few tiles in front of the lowered terrain tiles, drag road across the lowered terrain and the body of water until you get several tiles beyond the opposite shore. The road tiles should turn blue.

Step 4.
A bridge over soon-to-disappear waters. � 4. Now you should have a beautiful bridge. The bridge you get depends on how wide the span is.

Step 5.
Using the lowered terrain to level the terrain beneath the bridge. The mouse was clicked on the lowered terrain with the Level Terrain tool and dragged beneath the bridge. � 5. This is where it gets a bit tricky. What we'll end up doing is leveling the terrain beneath the bridge. To do this, though, you have to level the terrain with a specific height. This height is simply 13 meters below the starting ground level (the ground level that you started with). For example, if I initially started placing my water on terrain having an elevation of 52 meters, I would want to level the terrain with 39 meter terrain. To determine the starting ground level, query a tile on the surrounding land. Now to get land 13 meters below that, use the Lower Terrain tool near the to the side of the bridge. When you think you've lowered the terrain one notch, use the query tool and check its elevation. When you have a tile that's 13 meters below the rest of the tiles, use the Level Terrain tool to bring the land under the bridge to that level.

Step 6.
Our land bridge shore is purty, ain't it? What, where's the shore?!? � 6. If you did everything correctly, you now have a nice land bridge.

Note: You won't be able to build roads or rail under the land bridge. If the above procedures do not work for you, make sure you have sufficient funds to build everything and work with the terrain. Also, try repeating the steps several times before giving up. It's an exact science and can be reproduced 99% of the time. Double check all your steps.