Most people do not realize the amount of time and energy that goes into planning the construction of a structure. It is not as simple as deciding that you want to put something up and then hiring people to build it for you. There is actually a tremendous amount of preparation that takes place before a single shovel of dirt is moved.
First, a piece of land must be tested by a geotechnical engineer to make sure that it can withstand the pressure of the structure that is being built there. Once this is done the appropriate groundwork is laid out so that an appropriate foundation can be laid out. This will vary depending on where the building is and what external elements have to be taken into consideration. If you are building a structure in an earthquake zone, then you will need to compensate for this, and if you are building in a tornado prone zone you will need to make sure that you compensate for this as well.
These are all jobs for civil engineers, and that is why they are so important to construction. While an architect can design a building, the civil engineers must make sure that it is going to be feasible and structurally sound to construct it. These considerations must take place at every level of construction until the job is finished.