Just before Martello Avenue, past Park Road.  How they broke up the rock to create level platforms.

[05] Sandycove

This is an 11-stop audio guide to the popular walkway from Dún Laoghaire to Dalkey Quarry, known locally as "The Metals",
It's not just a journey through fascinating engineering and social history.  It's also an eye-opening excursion along a unique living piece of local heritage.
Join architectural historian Rob Goodbody, author of "The Metals", and producer Aileen O'Meara back to the days when Dún Laoghaire just a small fishing village surrounded by rocky outcrops, and hear the fascinating story of how engineers designed this unique trackway that shaped the development of this marine town and its fine harbour.