Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.096.

A pilgrim may spend the Day of Arafah anywhere within the bounds of Arafah for all of it is equally good for encamping (on this particular day) except the bottom of the valley called ‘Urnah to the west of Arafah. There is consensus that spending the Day of Arafah at ‘Urnah is not sufficient to fulfil the condition of staying at Arafah.

Spending time near the rocks or as close to them as possible is commended. The Prophet (peace be upon him) stopped at this place and said, “I have stopped here, but the whole of Arafah is a stopping place (for the Day of Arafah).” (Reported by Ahmad, Muslim, and Abu Daw’ud on the authority of Jabir) Climbing the Mountain of Mercy or the belief that standing on it is better than standing in any other place is wrong. Nor does doing so represent a sunnah of the Prophet (peace be upon him).