id: sig-20260722-report-cn066
site_id: gb-llanberis-dolbadarn
attribute: designation_report
value: 'Reference Number

  CN066

  Name

  Castell Dolbadarn

  Date of Designation

  Status

  Designated

  Unitary Authority

  Gwynedd

  Community

  Llanberis

  Easting

  258591

  Northing

  359806

  Broad Class

  Defence

  Site Type

  Castle

  Period

  Medieval

  The following provides a general description of the Scheduled Monument.

  The monument consists of the remains of a castle, dating to the medieval period. A castle
  is a defended residence or stronghold, built mainly of stone, in which the principal or
  sole defence comprises the walls and towers bounding the site. Some form of keep may have
  stood within the enclosure but these were not significant in defensive terms and served
  mainly to provide accommodation.

  Dolbadarn Castle was one of three castles begun by the Prince of Gwynedd, Llywelyn ap Iorwerth
  in the early thirteenth century to defend the passes into Snowdonia, together with Dolwyddelan
  Castle (CN040) and Castell y Bere (ME023). It sits on top of a steep‐sided rocky crag with
  good views up and down the valley and controlled the main routeway through the Llanberis
  Pass, and also guarded the economically important cattle pastures of the area.

  The masonry of the castle is of several periods: the earliest work is unmortared and consists
  of a simple curtain wall enclosing the summit of the rock, within which there were a number
  of rectangular structures, including a hall, with walls up to 1m thick. There is an access
  from the NE which comes into the large building on the N ‐ this is presumably original.
  A large, well-built round tower, with walls 2m thick, is a later addition dating from the
  1230s. Its first-floor entrance was originally reached by a timber stair and, unusually,
  the doorway was defended by a portcullis. Inside the tower, beam holes for the two main
  floor levels can be seen, as well as fireplaces. The basement was reached by a ladder and
  the second floor and roof via a circular staircase in which the spiral reverses direction
  halfway up. It is probable that this tower was where Llywelyn ap Gruffudd kept his brother,
  Owain ap Gruffudd imprisoned for two decades, from 1255 to 1277.

  The castle fell into English hands after the defeat of Llywelyn ap Gruffudd in 1282 and
  was soon supplanted by Edward I’s new fortification at Caernarfon (CN079), and so was partially
  dismantled and abandoned. Little is recorded concerning the castle after the early fourteenth
  century, though there is a suggestion that Owain Glyndwr used the castle to imprison captives
  circa 1400.

  The monument is of national importance for its potential to enhance our knowledge of medieval
  defence. It is a well-preserved and important relic of the medieval landscape. It retains
  significant archaeological potential, with a strong probability of the presence of associated
  archaeological features and deposits. The structures themselves may be expected to contain
  archaeological information concerning chronology and building techniques.

  The scheduled area comprises the remains described and areas around them within which related
  evidence may be expected to survive.'
source_url: http://cadwpublic-api.azurewebsites.net/reports/sam/FullReport?lang=en&id=2428
source_title: Scheduled Monument Full Report — Castell Dolbadarn
publisher: Cadw
observed_date: '2026-07-22'
collected_by: scripts/build_assessment_batch.py
confidence: high
notes: The designation text. Assess the six bands against THIS evidence only; omit any band
  it does not speak to.