Cefn Eglwysilan
hill (382m) in Rhondda Cynon Taf
Cefn Eglwysilan is a hill in South Wales, the twin 382m summits of which lie 2 km east of Pontypridd in Rhondda Cynon Taf county borough. Its eastern side lies within the community of Aber Valley in Caerphilly county borough.
Like neighbouring Mynydd Eglwysilan, the hill is named after the hamlet of Eglwysilan, the church here being dedicated to an obscure saint Ilan. A wireless transmission station is sited on the more northerly of the two summits (at OS grid ref ST 099911). The southerly one is crowned by a trig point.
Geology
The hill is formed from the Hughes Sandstone (formally the ‘Hughes Member’ and formerly the ‘Hughes Beds’) of the Pennant Sandstone Formation laid down late in the Carboniferous Period (c 309-306 million years ago). Siltstones and mudstones appear beneath the main upper bed of sandstone.
Archaeology
The linear earthwork known as Senghenydd Dyke stretches across the eastern side of the hill. It is considered to mark the edge of an extensive 13th century deer park associated with nearby Caerphilly Castle. Three cross dykes also sit on the summit plateau and further earthworks are evident on its southern flank.
“Cefn Eglwysilan” enters the record as hill (382m) in Rhondda Cynon Taf. Crown Archives preserves that source wording while asking what Cefn, Eglwysilan and hill can confirm, complicate or overturn.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated May 22, 2026. The linked authority identifier is Q16246181. Authority coordinates are 51.606, -3.305. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Cefn Eglwysilan” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.