The Deer Park was landscaped by the
Fitzwilliams
in the 1700s.
"Beyond the house to the west, across a smooth lawn, is a thick wood,
intersected with walks and adorned with temples
and rural structures of various kinds,
while through the park stretch away two drives,
one disused and grass-grown leading under an archway of noble trees
to Foster's Avenue,
and the other, commanding lovely views of Dublin and its bay,
leading to Mount Anville and Dundrum."
- [Ball, vol.2, 1903].
This westward-headed drive is possibly the walk in the Deer Park
that runs along the N boundary of the park
from the church to the Mt Anville gates.
It seems that this ordinary park walk is over two hundred years old.
"Deerpark" is now a public park, opened to the public in 1971.
"A second double avenue of great elms still marks the road
which leads to Merrion Castle by way of Foster avenue,
a relic of the days when my Lord Viscount Fitzwilliam rode up from
his stronghold, down by the sands of Dublin Bay,
to hunt the stag in the hills."
- [Wilkinson, 1925].
This is presumably now North Avenue.