Read these two articles about this walk:
https://newengland.com/travel/massachusetts/sconset-bluff-walk-nantucket-ma/
AND:
https://www.nantucket-ma.gov/facilities/facility/details/sconset-bluff-walk-25
One of the best walks in all of Nantucket if you are a house "lookie loo" like me.
It starts on the Sconset bridge then eventually winds along the cliff off of the ocean and meanders along public access behind all of these beautiful Sconset homes. The path is only really marked by obvious tracks of those who walked it before you. And you will see others coming the other way as you walk.
It is perfectly legal public access, so don't worry.
Eventually erosion forces you onto the road, it is pretty clearly marked off and that road to the right leads to the Sankaty Head lighthouse. (another Nantucket gem.)
Then we walked the actual road back to Sconset center to see the houses from the other side.
Out and back it is about 4 miles total. No real hills to worry about.
A beautiful walk, old expensive homes on one side and the ocean on the other! read more