Allt Cwm-tywyll (Unclassified).
Grid Reference: SN 44464 44308. Parish: Llandysul, Cardiganshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Allt Cwm-tywyll (Topographic feature).
Grid Reference: SN 84647 35813. Parish: Llanfair-ar-y-bryn, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Bryngolen or Cwmtywyll (Field).
Grid Reference: SN 44564 43911. Parish: Llandysul, Cardiganshire
When recorded: Circa 1840. Primary Source: none. Secondary Source: Cynefin

Bryngolen or Cwmtywyll (Field).
Grid Reference: SN 44524 43663. Parish: Llandysul, Cardiganshire
When recorded: Circa 1840. Primary Source: none. Secondary Source: Cynefin

Bwlch Tywyll (Field).
Grid Reference: SH 74956 49556. Parish: Penmachno, Caernarfonshire
When recorded: Circa 1840. Primary Source: none. Secondary Source: Cynefin

Cae Porth-tywyll (Unclassified).
Grid Reference: SN 63454 32799. Parish: Talley, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

CAE-PANT-TYWYLL (Unclassified).
Grid Reference: SO 04080 06731. Parish: Merthyr Tydfil, Glamorgan
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Coed Lletgr-tywyll (Unclassified).
Grid Reference: SN 89099 53669. Parish: Llanfihangel Abergwesyn, Brecknockshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Cwm Tywyll (Unclassified).
Grid Reference: SJ 04887 33574. Parish: Llandrillo-yn-Edeirnion, Merionethshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Cwm-tywyll (Settlement).
Grid Reference: SN 40891 39422. Parish: Llangeler, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website