If you are interested in designing buildings or other structures, then you are at the right place.
Civil engineering is a general category that includes other sub categories like the following: Transportation, Structural, Environmental and Water Resources, Geotechnical, Material Science etc., Many times these branches are intertwined with each other or depend highly on one another.
Civil: Transportation engineering-Covers all subjects related to transportation projects like designing layout of roadways, railways, highways, bridges, entry and exit ramps to bridges etc. They actually set the layout of the curves both horizontal and vertical geometry of the bridge structure.
Civil: Structural engineering-The engineers who specialize in Structural engineering actually get to design the structures like buildings, bridges, tunnels, marine structures like wharves, etc. Again once the basic structural design is learnt it can be applied in a variety of scenarios. Structural engineers make sure that the structure they design will be safe and follow all the rules and regulations set by the various code agencies.
Civil: Environmental-This branch of engineering covers all things that make the design environmentally friendly. Ranging from materials that are renewable, waste water engineering, impact of project on the ecology etc. There is a lot of fluid dynamics involved in water resources engineering.
Civil: Material science engineering-Specializes in material testing and latest advancements in engineered products that are sustainable and renewable. Some universities offer this closely related with Chemical engineering.
Civil: Geotechnical engineering involves the study of the geology of the earth and how the foundations of structures need to be designed to withstand seismic effects of the shifting ground. Also the Geotechs measure the location of water table and types of soils and how they interact with the foundation. Structural and Geotechnical engineers work closely in designing a structure foundation.
Civil: Construction-specializes in actually making the design come alive in the field. They deal with project management, construction sequencing, cost management etc.
If you are looking for who gets a say in the looks of the buildings, then you have to look into Architecture. Many Architectural and Civil Engineering departments are close to each other. Most architects learn the basics of engineering but don’t get in depth with the actual design part of it. Most of the time Architects set the looks and structural engineers make it happen. It is definitely a love-hate relationship between the Architects and Structural Engineers. I like to say it is similar to left brain right brain analogy. The architect is the right brain (creative side) and the structural engineer is the left brain (logical and mathematical side). You kind of need both hemispheres of the brain to make anything happen.