That sounds like lens flare...
Does it look like the object in the lower portion of this image?
If so, it's usually just a matter of shading your lens with a lens hood. If one didn't come with your lens, a matching hood is available to purchase separately. Just search by your lens designation or look it up at the Canon website. Be careful, though... because different versions of lenses might use different hoods.
The above was a test done with my EF-S 10-22mm lens when I first got it. The matched lens hood for it is very large and I was hoping to use the lens without it. I thought that might be possible, since the 10-22mm lens is unusually resistant to flare. However I decided to carry the lens hood with me and use it (like I do with all my lenses), after seeing the difference it made (below)...
Flare problems also can be caused or amplified by cheap "protection" filters that people put on their lenses. If you have a filter on the lens, try again without it.
***********
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
FLICKR & ZENFOLIO
Yep, those are definitely lens flare.
You might be able to reduce it by...
1. If you don't already have it, get and use the correct hood for your lens.
2. If you have any filters on the lens, remove them.
3. If you must use a filter for some purpose (such as ploarization), be sure it's high quality, multi-coated,...But still only use filters when they serve a purpose. Added layers of glass give more surfaces for flare to reflect..
4. Watch for flare occuring in your viewfinder and slightly reposition yourself and/or the camera & lens to reduce it.
5. Generally be aware of the position of the sun and try to avoid shooting directly at it. In other words, keep the sun behind you as best you can (in both your examples, shooting at a different time of day would have solved the problem).
6. Any strong light source that's directly striking the glass elements of a lens can cause flare effects. It's not limited to the sun alone.
As Tim noted, some people actually incorporate various types of lens flare deliberately in their images. In fact, there are image editing software that ADD flare to images.
A different lens might be less prone to flare... But all lenses do it to some degree or another. Below were shot with very high quality Canon EF 24-70mm f/2.8L lens (with it's lens hood and without any filter). To reduce the flare in the second image, the only difference was was moving camera and lens slightly. It was easy to see in advance in the viewfinder,, what the difference would be in the images.
