IIArvon and adjoining outbuildings to the north Situated in a prominent position at the junction of Heol Buddog and Ffordd-y-Sir with gardens in front and the similarly detailed Bod Owen alongside, the highly patterned slate roofs of Arvon and its
IIBarn and stables at Eithinog-uchaf Located at an oblique angle on the north side of the farmyard at Eithinog-uchaf; the farmyard sits to the north of the farmhouse on the track to Pant Eithinog, which itself lies just off Ffordd Clynno
IIBarn to north of Taldwrst Situated at the northern end of the farm at Taldrwst on a track leading south of Lon Dwr, approximately 1.5 km east of Llanllyfni.
IIBarracks Building Located to the south-west of the quarry offices on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.
IIBethel Chapel, railed enclosure and gates Prominently situated on slightly rising ground, into which it is set, towards the northern end of Penygroes, its Sunday School on the other side of the road, the chapel sits in its own walled and rail
IIBod Owen Situated in a prominent position at the junction of Ffordd-y-Sir and Heol Buddog with gardens in front and the similarly detailed Arvon alongside, the highly decorated slate roof of the building forms
IIBryn Deulyn Located on bend in narrow road at eastern entrance to Dorothea Slate Quarry with hooped iron railings on low entrance walls swept to left side to enable easy vehicular access.
IIBryn Eglwys Located in the village of Llanllyfni on the south-east side of Ffordd Rhedyw (Rhedyw Road) directly opposite the Church of St Rhedyw.
IIBryn-mawr Situated in small pasture fields overlooking sea on rough track approximately 300m west of Pant Eithinog.
IIBrynarvon Situated on track (Weirglodd-newydd) immediately above Talysarn.
IIBryngwdion Located in pasture fields at the end of a farm track running off the east side of the minor road, which turns off the A 499 towards Pont-y-cim; the farmhouse sits to the west of its farmyard.
IIBwthyn Located on the south side of the B 4418 at the foot of a rock face directly opposite the Chapel.
IICae-efa-lwyd-fawr Located at the end of a farm track off the north side of Ffordd Clynnog (Clynnog Road) about 1km west of Penygroes.
IICapel Drws-y-coed and Ty Capel Set in an isolated position at the foot of Craig y Bera on the north side of the B 4418, fronted by spear-headed iron railings and central gate on a low rubblestone wall with piers to the gates and en
IICauseway Located off the B 4418 to the north of Dorothea House, beginning beyond Pont Wythdir and running north-east for approximately 100m across marshy ground with a spoil heap to the north-west on the south
II*Church of St Rhedyw Prominently sited on a corner on Ffordd Rhedyw within a raised rubble-walled churchyard on sloping ground down towards the Afon Lyfni.
IICoach house/wash house and stables at Bryn Deulyn Located in grounds of Bryn Deulyn to south of house; set into a bank with the massive waste tip of the former Dorothea Slate Quarry immediately behind.
IICoedcae-du Located at the end of a track, directly below the embankment of the former London and North-West Railway, approximately 0.4km south-east of Llanllyfni.
IICompressor House Sited higher up the slope away from the other buildings on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.
IICowhouse at Eithinog-uchaf Located on the east side of the farmyard at Eithinog-uchaf; the farmyard sits to the north of the farmhouse on the track to Pant Eithinog, which itself lies just off Ffordd Clynnog.
IICowhouse/granary and pigsties at Eithinog-uchaf Located on the south side of the farmyard at Eithinog-uchaf; the farmyard sits to the north of the farmhouse on the track to Pant Eithinog, which itself lies just off Ffordd Clynnog.
IIDisused cottage to south-west of Llwyndu Canol Situated in a lowland position in pasture fields to the north of Ffordd Llwyndu (Llwyndu Road), a minor road running from Penygroes to Carmel.
IIDol-wenith Located in a low-land position on the eastern side of Lon ty Gwyn, a minor no-through road running eastwards from Llanllyfni.
IIDrying House Located on Level VIII (Bonc Brig) of the Pen-yr-Orsedd Slate Quarry at the foot of the modern steep access road from Y Fron.
IIEisteddfa-isaf Set back from the road within its own original field system close to the ruins of a former water mill.
IIEithinog-uchaf Situated in lowland pasture fields at the end of a farm track off the south-west side of Ffordd Clynnog (Clynnog Road).
IIEngine and Compressor House Located on Level VIII (Bonc Brig) of the Pen-yr-Orsedd Slate Quarry towards the foot of the modern steep access road from Y Fron.
IIEngine House Located on Level VIII (Bonc Brig) of Pen- yr-Orsedd Slate Quarry at the foot of the modern steep access road from Y Fron.
IIEngine House Located to the north-west of the Eureka slate mill on Level VIII (Bonc Brig) of Pen-yr-Orsedd Slate Quarry.
IIEngine House Located on Level VIII (Bonc Brig) of Pen-yr-Orsedd Slate Quarry at the foot of the modern steep access road from Y Fron.
IIEureka Slate Mill Located on Level VIII (Bonc Brig) of Pen- yr-Orsedd Slate Quarry immediately to the north-east of the slate steps leading down to Level VI (Bonc yr Offis).
IIHafod-y-llyn Moorland-edge location, the smallholder's cottage and cowhouse sit within their original small field system and are reached by a long rough track.
IIHen-dy Located on the west side of Ffordd Haearn Bach (the old tram road) approximately 200m north-west of Pen-y-Groes.
IIIndependent Chapel Located on the eastern side of the village street with the manse (Ty Capel) directly adjacent, the chapel is approached by a driveway flanked by low stone walls.
IIK8 Phonebox, Nebo In the small hamlet of Nebo, adjacent to Glan Gors Uchaf, Ffordd Nebo LL54 6EF.
IILocomotive Shed Located on Level VIII (Bonc Brig) of the Pen-yr-Orsedd Slate Quarry to the east of the modern steep access road from Y Fron.
IILocomotive Shed Located immediately to the north of the incline and drumhouse at the south-east corner of Level VIII (Bonc Brig) of Pen-yr-Orsedd Quarry.
IILocomotive Shed Directly adjoins the drumhouse on Level IV (Bonc Isa') of Pen-yr-Orsedd Slate Quarry.
IIMaes Mawr Located in a low-land setting at the end of a track off Lon Ty Gwyn approximately 0.5km south-east of Llanllyfni.
IIMilestone Located on the south-east side of Ffordd Rhedyw (Rhedyw Road) in Llanllyfni to the north-east of the Church of St Rhedyw; set in a rubblestone boundary wall.
IIMilestone Located on the north side of the B4418 directly opposite Tai Victoria (Victoria Terrace) approximately 0.5km east of Nantlle; set in a rubblestone boundary wall.
IIMilestone Located on the east side of the A 487 on the northern edge of Penygroes; set in a rubblestone boundary wall.
IIMilestone Located on the east side of the A 487 approximately 3.2km south of Llanllyfni; set in a rubblestone boundary wall.
IIMilestone Located on the east side of the A 487 approximately 1.6km south of Llanllyfni; set in a rubblestone boundary wall.
IIMilestone Located on the north side of the B 4418 between Drws-y-coed and Nantlle; set in front of a rubblestone boundary wall.
IIMuriau & Muriau Stores Located in the centre of Penygroes on the west side of Heol-y-Dwr (Water Street) near the junction with Lon Pitar.
IIPant Du Situated in a lowland position within pasture fields at the end of a short track off the south side of Hen Lon to the east of Penygroes.
IIParc Set within its original small field system on a track on the western edge of the small settlement of Cilgwyn.
IIParc Set on south side of road within original small field system approximately 100m south-west of the Independent Chapel, Nasareth.
IIPen-y-bryn Located at the end of a track on the north side of the old Talysarn to Nantlle Road.
IIPen-y-bryn-bach Located at end of track in pasture fields approximately 600m north-east of Ffordd Clynnog.
IIPenbryn Mawr Set at the end of a track in pasture fields approximately 45m from Ffordd Clynnog. A menhir stands a little to the south-east of the house.
IIPenyrorsedd War Memorial At the front of the yard of Capel Baladeulyn, set behind the chapel walls and railings.
IIPigsties at Bryngwdion Located immediately to the west of the farmhouse at Bryngwdion.
IIPont Factory Road bridge and causeway on the A 487, spanning the Afon Lyni, between Llanllyfni and Penygroes.
IIQuarry Hospital Located to the south-east of the quarry offices on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.
IIQuarry Offices Located between the store building to the north and the barracks to the south-west on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.
IIRopeway Winding House (north-east) Located immediately to the north-west of the slate mill on Level IV (Bonc Isa') of Pen-yr-Orsedd Slate Quarry.
IISeion Congregational Church Situated in an elevated position amidst terraced housing approximately half way up Cavour Street; in front of the chapel is a small forecourt behind an irregularly coursed rubblestone wall, topped by
IISlab Mill Directly adjoins the large slate mill on Level IV (Bonc Isa') of Pen-yr-Orsedd Slate Quarry.
IISlate Mill Directly adjoining the slab mill to the south on Level IV (Bonc Isa') of Pen-yr-Orsedd Slate Quarry.
IIStore Building Located between the former slate mill to the north-east and the quarry offices to the south-west on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.
IIStrainer arches and retaining walls Located to the south of Pen-y-bryn, the strainer arches and walls retain the slate waste tips flanking the route of the Dorothea Quarry branch of the former Nantlle Railway.
IITurnpike Located on the north side of the B 4418 approximately 500m east of Penygroes.
IITy Capel Located on the eastern side of the village street, from which it is set back, with the Independent Chapel it serves directly adjacent.
II*Ty Mawr Located at the western end of Nantlle near the eastern entrance to the Dorothea Slate Quarry.
IITy Mawr Approximately 250m north of Nebo, set back to the south of the road within original small field system.
IITyn-llwyn Low-land farmhouse located near disused quarry approximately 1km east of Llanllyfni.
IIWeighbridge House Located directly adjacent to the locomotive shed immediately to the north of the incline and drumhouse at the south-east corner of Level VIII (Bonc Brig) of Pen-yr-Orsedd Quarry.
IIWeirglodd-newydd Situated on track (Weirglodd-newydd) immediately above Talysarn.
IIWinding Drumhouse Located to the south-east of the slate mill on Level IV of Pen-yr-Orsedd Slate Quarry above the remains of the incline leading down to the start of the former Nantlle Railway below.
IIWinding Drumhouse and Incline Located to the south-east of the slate mill on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry, the drumhouse is dramatically sited at the head of the incline running downhill to the south-east
IIWinding house Located on Level VIII (Bonc Brig) of Pen-yr-Orsedd Slate Quarry to the east of the Eureka Slate Mill.
IIWorkshops Located to the south of the slate mill on Level VI (Bonc yr Offis) of Pen-yr-Orsedd Slate Quarry.