The Glen Rock is a 570-ton glacial erratic — a boulder deposited by retreating glaciers at the end of the last ice age — sitting in a small park near the town centre. It is neither grand nor spectacular, but it is genuinely old and is the thing Glen Rock is named after, which gives it a certain local significance.
The rock sits near the intersection of Maple and Rock avenues, alongside the Glen Rock train station. You can walk around it, read the historical marker, and reflect briefly on glaciology before returning to your day. It is the kind of thing that passes unnoticed by residents but reliably fascinates anyone who has just learned about glacial erratics.