Ski slopes come in all sorts of varieties. Some are fierce and steep, while others are mellow and meandering. Classification systems tend to vary from country to country, so it's important to make sure you know which symbol to look for at the head of a trail or you could find yourself in a world of trouble on the way to the bottom.
Some of the factors that ski resorts use to rank their runs include the grade, or steepness, of the trail, the width of the trail, recent snow conditions and the amount of grooming the trail receives.
In the United States, the three most common trail ratings are green circles, blue squares and black diamonds. Green circles are the easiest slopes, skiable by most beginners, while blue squares are generally for intermediate skiers and black diamonds are best left to the pros. In Europe things are a little different. European ski resorts tend to label all their runs with circles, with difficulties ranging from piece-of-cake greens through beginner blues, intermediate reds and expert blacks. Luckily for any U.S. skiers traveling abroad who might be unaware of these subtle differences, green and black still both respectively signify the easiest and most difficult runs.
Depending on where you're skiing, you might also spot an elusive double (or even triple!) black diamond trail, which are usually as steep, narrow and ungroomed as regular black diamonds, but sport even more challenging features like massive moguls, drop-offs or tree-clogged intervals. There are a few other ways you might see ski slopes classified, too. In Europe, for example, yellow often lets skiers know the trail hasn't been groomed, which can make skiing more of a challenge. Terrain parks -- areas that feature extras like jumps, jibs and half-pipes -- are often labeled with orange ovals or rounded-off rectangles in the United States.
It's also important to keep in mind that different resorts often have different interpretations of which trails should fall into which categories, so it can be a good idea to do a little homework before you hit the slopes -- otherwise you could be the one doing all the falling.