The Grand Couloir is located between the Tete Rousse and Gouter Huts on the Normal Route to Mont Blanc. It is known for its stonefall in dry conditions when there is not enough snow to hold the loose rocks from tumbling down the couloir.
We traverse it at about the third of the way between the two huts. Only there, a relative danger of stonefall that can seriously endanger climbers. Crossing it in the early morning is usually the safest, but it depends on the season. If there is very little snow, it might not even be worth risking it. Most of the time, the danger is minimal. We still take this decision seriously and will only decide to go on with the climb if the conditions are good enough.