Ancient Monuments

History on the Ground

This site is entirely user-supported. See how you can help.

Castell Tomen y Mur

A Scheduled Monument in Maentwrog, Gwynedd

We don't have any photos of this monument yet. Why don't you be the first to send us one?

Upload Photo »

Approximate Location Map
Large Map »

If Google Street View is available, the image is from the best available vantage point looking, if possible, towards the location of the monument. Where it is not available, the satellite view is shown instead.


Latitude: 52.93 / 52°55'47"N

Longitude: -3.9254 / 3°55'31"W

OS Eastings: 270675

OS Northings: 338687

OS Grid: SH706386

Mapcode National: GBR 5Z.MDXW

Mapcode Global: WH55P.NMY5

Entry Name: Castell Tomen y Mur

Scheduled Date:

Source: Cadw

Source ID: 3195

Cadw Legacy ID: ME002

Schedule Class: Recreational

Category: Amphitheatre

Period: Roman

County: Gwynedd

Community: Maentwrog

Traditional County: Merionethshire


Tomen y Mur is a Roman military landscape on upland slopes overlooking the Trawsfynydd basin. The large scheduled area comprises two scheduled monuments (ME002 and ME078) in four adjoining parts, containing several specific sites, although adjacent and intervening areas are also scheduled.

In summary, the main elements are: A fort, at SH70603865 Earthworks SE of the fort including a bath-house at SH70693855 and a probable mansio (accommodation for travellers) at SH70713857, and a bridge abutment, at SH70733852 A medieval motte, constructed over part of the Roman fort, at SH70553868 A vicus (civilian settlement) NE of the fort, at SH70693877 A ludus or amphitheatre NE of the fort, at SH70813890 Barrows ENE of the amphitheatre, at SH70893891 A parade ground ENE of the fort, at SH70813875 A mound SE of the parade ground at SH70893864, with other earthworks SW of this at SH70853865 and possible leats E of the parade ground Barrows beside the road SE of the fort, at SH70953827, SH70923833 and SH71023816 and in the same area, the remains of two possible marching camps SH7098 3832 A fort annexe and two practice camps at SH70433878 and SH70423871 and a medieval homestead enclosure at SH70393881, to the NW of the fort.

The following descriptions come from various published sources and notes made by Cadw Field Monument Wardens.

The fort The fort stands in a commanding position on a low spur with wide views over the Vale of Ffestiniog to the NW and the undulating country to the S. It had two main structural phases. The earlier fort had earth and timber defences consisting of two banks topped by a timber palisade. Between the banks there were initially two ditches, but these were later replaced by a single ditch. This fort was probably constructed as a result of the campaign of the general Agricola, during the period that Julius Frontinus was governor of Britain, between AD74 and AD78, when the system of forts linked by roads was first established in NW Wales. The early fort forms a rectangle some 158m by 110m internally, with its long axis sloping downhill from NW to SE. The NW defences of this fort survive as low earthworks about 30m beyond the defences of the later, reduced fort. The second phase fort, probably constructed in about AD120 when Hadrian was emperor, had an internal area of 122m by 110m and was defended by a stone wall, as well as the existing earth banks and ditches. On three sides the wall stood on top of the earlier inner bank, but on the NW a new ditch was dug and bank created. Squared stones taken from the wall can be seen in the abandoned farmstead to the N of the fort and in field walls around the site. The stone could have been quarried at several places below and to the SW of the fort. Ten ‘centurial stones’ have been found at Tomen y Mur. They are inscribed in Latin and commemorate the building of sections of the wall by different groups of soldiers. Like most forts in north Wales, it was abandoned by AD135. The defences of this second phase now appear as banks surmounted by modern field walls, and the interior of the fort is level with the tops of the banks. The motte is built astride the centre of the NW side of the reduced fort, and may well cover and preserve the gate that must have existed at that point. The other three gates have been largely destroyed, but their positions can be made out, and at the SE gate are the remains of guard chambers, the central pier and stone blocking. Geophysical survey shows the internal layout of the fort in impressive detail. It has been suggested that three Roman roads approach the fort, from the NW, NE and SE. In addition, a feature similar to an agger (a raised causeway for a road), 50m long, 15m wide, 0.6m high and orientated NW-SE has been recorded in line with the centre point of the NW side of the fort.

Earthworks SE of the fort including a bath-house, a probable mansio (accommodation for travellers), and a bridge abutment

On land sloping down from the SE wall of the fort to the stream are firstly a series of three terraces. Next, a levelled rectangular area defined by a low bank, which has been interpreted as the site of a post-Roman building as it partially overlies the road. Beyond, and either side of the road, which runs at an angle of about 15 degrees S from the SE gate, are a bath-house disturbed by 19th century excavations and low banks forming the remains of a three-room courtyard structure, probably a mansio. The road continues to an abutment for a bridge across a stream in a narrow gorge and beyond.

The medieval motte The name Tomen y Mur derives from the Norman motte (castle mound) of stone and earth, upon which once stood a timber tower. Tomen y Mur was used when William II (William Rufus) and Henry I campaigned against King Gruffydd ap Cynan of Gwynedd in the 11th-12th centuries. The motte is about 10m high and is surrounded by a ditch 4m wide, with a counterscarp bank surmounted by a modern field wall. The top is uneven, with two principal hollows on the SE and SW which may represent the sites of original buildings (or possibly robbing). It is slightly oval, measuring approximately 14m N-S by 19m E-W. The second phase Roman fort was likely used as the bailey, however, a slight bank to the NE of the motte may be the remains of an inner bailey.

The vicus (civilian settlement) NE of the fort Archaeological surveys have shown that there was a small vicus (civilian settlement) either side of the road on the NE side of the fort. This probably consisted of shops and workshops, houses and gardens.

The ludus or amphitheatre NNE of the fort The amphitheatre was probably used principally as a facility for training soldiers, but possibly also for entertainment. It consists of an oval earthwork with internal diameters of 28m N-S by 23m E-W. A bank of grassed-over stone 1.5m-2m high and c.8m wide runs around the perimeter and the interior is level. A field wall has been built across it and it has been damaged by a 19th century quarry tramway, the lane and a track.

Barrows ENE of the amphitheatre On a low knoll ENE of the amphitheatre and close to the assumed line of the Roman road heading N are what are thought to be Roman burial barrows. Two appear as low, grassy mounds with square ditches around them, a later bank runs between them. One mound is 6m across and the other 4m across, the ditches around them are about 1.5m wide and 0.2m deep. There may be others nearby.

Parade ground To the E of the fort are the remains of a large platform, approximately 120m by 110m, which has clear banks on the SW and SE sides, that on the SE measuring 0.7m high and 3-4m wide, the interior is partially levelled. It is interpreted as a partially completed parade ground.

A mound SE of the parade ground, with other earthworks SW of this and possible leats E of the parade ground To the SE of the parade ground is a mound in the shape of a truncated pyramid, 15m square at the base, 8m square at the summit and 3.5m high. Projecting to NE and SW are level-topped banks 25m in length, 10m wide and 1.5m high. It has been variously interpreted as the site of a monument, a tribunal (a raised platform for a commanding officer) and a temple complex and alternatively dismissed as a natural hillock. It may be a natural feature that has been enhanced. SW of this feature (and S of the parade ground) are a series of small rectangular enclosures bounded by low earth banks. They may be contemporary with the Roman occupation, but are probably later. To the E and S of the parade ground is a leat which once carried water to the bath-house, it is 1m wide and 0.2-0.3m deep. A second leat, for carrying water to the fort runs to the N.

Barrows beside the road SE of the fort, and in the same area, the remains of two possible marching camps Beside the road some 450m SE of the fort is a mound interpreted as a Roman burial barrow, showing signs of having been robbed. It is square in plan with sides measuring between 10.7m and 11.6m long, around which is a level berm, then a square ditch 3m wide and 0.6m deep with an external bank. Adjoining it on the NW are the remains of another, much smaller barrow. Two other small barrows once lay along the road to the NW, but have been ploughed out. Further to the SE is another mound, which may be Roman or prehistoric in date. Surrounding the barrow on a large square platform, the remains of what have been interpreted as two superimposed marching camps can be seen on air photographs.

A fort annexe and two practice camps and a medieval homestead enclosure to the NW of the fort A fort annexe on the NW side of the fort was discovered by geophysical survey. The practice camps are small, square enclosures, bounded by a bank and ditch, although only one is now visible, measuring 13m across. The Ordnance Survey suggested the presence of a Roman field system in this area, comprising low banks and traces of ditches; a medieval homestead enclosure measuring 40m by 25m lies on a steep N facing slope.

The fort is referred to as Mur y Castell in the Mabinogion, there is a tradition, based on the tale of Math fab Mathonwy, this was also the site of an early medieval llys (a royal court of the Princes of Gwynedd), but this has not been confirmed by archaeological excavation.

The monument is of national importance for its considerable potential to enhance our knowledge of Roman military organisation and medieval fortification practices. The monument forms an important element within the wider context of the Roman and Norman occupation of Wales and retains significant archaeological potential. The structures and buried deposits may contain well preserved archaeological evidence concerning chronology, layout and building techniques, along with environmental evidence.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

Other nearby scheduled monuments is an independent online resource and is not associated with any government department. All government data published here is used under licence. Please do not contact for any queries related to any individual ancient or schedued monument, planning permission related to scheduled monuments or the scheduling process itself. is a Good Stuff website.