Mt Hotham has also rightly earned its reputation as being a true skiers mountain due to its vast amount of challenging terrain from hidden gullies and tree skiing, to steep cliff faces and vertical drops. Many of these areas are off piste and are accessed within and outside of the patrolled ski area. The area outside the official ski resort boundary is referred to as backcountry or side-country when directly next to the boundary perimeter.
Individual runs or piste ('trail', 'track') are graded by difficulty using ratings. Such trails are typically groomed, the exception being mogul runs. There are many areas within the ski resort that are never groomed and are considered off piste. Many of these areas have names though are not always detailed on lift company trail maps.
A colour shape rating system is used to indicate the comparative difficulty of trails. Ski resorts assign their own rating to runs, although make use of the guidelines (see below). On occasion, in the even of weather causing the snow conditions to alter (e.g., the formation of hard ice) the run difficulty level can be upgraded. Such decisions are made by the ski patrol and any changes will be clearly marked and identified.
The easiest slopes at a mountain. Generally, Green Circle trails are wide and groomed, with slope grades ranging from 6% to 25% (a 100% slope is a 45 degree slope)
Intermediate difficulty slopes. Generally, Intermediate trails are groomed, with grades ranging from 25% to 40%. Blue Square trails make up the bulk of pistes at most ski areas, and are usually among the most heavily trafficked.
Amongst the most difficult slopes at a mountain. Generally, Black Diamond trails are steep (40% and up) and may or may not be groomed.
These trails are even more difficult than Black Diamond, due to exceptionally steep slopes and other hazards such as narrow trails, exposure to wind, and the presence of obstacles such as steep drop-offs or trees. They are intended only for the most experienced skiers.