Granny Rock, Bayview Road, Ballycastle, Co Antrim is a listed building in the Causeway Coast and Glens local planning authority area, Northern Ireland.

Granny Rock, Bayview Road, Ballycastle, Co Antrim

WRENN ID
guardian-gateway-onyx
Grade
Local Planning Authority
Causeway Coast and Glens
Constituency
North Antrim MP: Jim Allister (TUV)
Country
Northern Ireland
Irish grid reference
D 120 414
Coordinates
55.20749, -6.24037
Source
NI Environment Agency listing

Also on this page: radon risk · weather exposure · detailed attributes ↓

Description

This is a prominent geological rock formation, likely dating back before 1600, now situated within the Town Parks townland of Ballycastle, County Antrim. The rock, known as Granny’s Rock, is a large, black outcrop that projects significantly from a base of concrete. It rises as an impressive column from a concrete concourse designed to improve access to the harbour. A commemorative granite plaque is set into the base of the rock, marking the historical experiments in telegraphic communication carried out by Marchese Marconi and George Kemp. Prior to harbour improvements, the rock was situated so that waves would lap against it. The Ordnance Survey map of 1832 does not name the rock, although the 1856 revision introduces the name “Granny’s Rock” and suggests it may have served as a coastguard flag signal point at that location. The plaque was originally erected in July 1973 and was relocated on 24th July 1998, likely during the harbour construction. Marconi and Kemp used the rock as one of several test sites to achieve a signal from Rathlin Island. The rock is now fully encompassed within the concrete concourse created as part of the harbour improvements. The site is located within the Ballycastle Conservation Area.

Local climate

Granny Rock, Bayview Road, Ballycastle, Co Antrim sits in one of the wettest parts of the UK, with an average of 1,340 mm of rain a year. This makes it wetter than 96% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 97% of listed buildings.

It experiences an average of 1 freeze-thaw cycle a year, fewer than 99% of listed buildings. Of these, 1 follows at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.2°C per decade since 1991.

Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.

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  • Weather exposure and heating demand — rain and frost month by month and year by year, wind direction, solar and humidity
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