South portal of former railway tunnel beneath Castle Square is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 3 May 2002. Railway portal.

South portal of former railway tunnel beneath Castle Square

WRENN ID
inner-merlon-hawthorn
Grade
II
Local Planning Authority
Gwynedd
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
3 May 2002
Type
Railway portal
Address
South portal of former railway tunnel beneath Castle Square, Caernarfon
OS grid reference
SH 479 625
Coordinates
53.13873, -4.274
Source
Cadw listing

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

Description

The south portal of the former railway tunnel beneath Castle Square is constructed from snecked rock-faced stone and dates back to 1869. This entrance features a cast iron girder that supports jack arches within the tunnel, which is inscribed with 'de Winton & Co 1869'. Above the entrance, there is a thick roll-moulded band and modern railings positioned above the coping stones. The opening is flanked by shallow buttresses; the left-hand buttress is set back from the end, while the right-hand buttress is integrated into the revetment wall beneath Segontium Terrace. The left side wall includes four recesses with brick arches beneath a roll-moulded band that continues from the entrance elevation, topped with coping stones and railings.

Local climate

South portal of former railway tunnel beneath Castle Square sits in one of the wettest parts of the UK, with an average of 1,370 mm of rain a year. This makes it wetter than 97% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 98% of listed buildings.

It experiences an average of 20 freeze-thaw cycles a year, fewer than 78% of listed buildings. Of these, 9 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°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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