A rock outcrop on its northwestern ridge is known as The Nubble, but topographic maps identify the formation as Haystack Mountain.

[2] Nubble Peak is flanked to the south by North Twin Mountain.

The mountain is officially trailless and is one of New England's hundred highest summits.

Nubble Peak stands within the watershed of the Ammonoosuc River, which drains into the upper Connecticut River, and into Long Island Sound in Connecticut.

The northwest side of Nubble Peak drains into Haystack Brook, thence into the Ammonoosuc.