Tons and tons of shells where fired during the 4 years of warfare. Large calibers, small calibers, mines, hand grenades in all shapes and sizes, shells filled with gas, rifle ammunition and so on. Of the artillery shells, not all shells exploded. Many of these can still be found on the battlefields today. Because the conflict happened so long ago, many people believe that the ammunition is safe and that nothing can happen to it anymore. In fact the opposite is true! The powder inside has become very unstable, the fuses still work, the shells and grenades can still explode and gas can escape from the gas cannisters.
So please leave any ammunition or fuses you find alone. If you want to take them home as a souvenir, be wise and only take a picture. People still get killed or severly wounded as a result of unskilled handling of ammunition!