Allt Derlwyn (Topographic feature).
Grid Reference: SN 45371 30464. Parish: Llanllawddog, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Bryn Derlwyn (Unclassified).
Grid Reference: SN 95320 99421. Parish: Carno, Montgomeryshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Bryn derlwyn (Field).
Grid Reference: SN 95331 99388. Parish: Carno, Montgomeryshire
When recorded: 1841. Primary Source: none. Secondary Source: Cynefin

Cae pen derlwyn (Field).
Grid Reference: SN 95634 98750. Parish: Carno, Montgomeryshire
When recorded: 1841. Primary Source: none. Secondary Source: Cynefin

Caer derlwyn (Field).
Grid Reference: SN 77610 01328. Parish: Blaenhonddan, Glamorgan
When recorded: 1841. Primary Source: none. Secondary Source: Cynefin

Caer Derlwyn (Field).
Grid Reference: SN 76102 01322. Parish: Blaenhonddan, Glamorgan
When recorded: 1841. Primary Source: none. Secondary Source: Cynefin

Cae'r Derlwyn (Field).
Grid Reference: SN 76130 01509. Parish: Blaenhonddan, Glamorgan
When recorded: 1841. Primary Source: none. Secondary Source: Cynefin

Careg y Derlwyn (Unclassified).
Grid Reference: SN 80699 70926. Parish: Ysbyty Ystwyth, Cardiganshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Cefn Derlwyn (Unclassified).
Grid Reference: SN 92694 47512. Parish: Treflys, Brecknockshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Coedcae y Derlwyn (Unclassified).
Grid Reference: SN 88441 01344. Parish: Glyncorrwg, Glamorgan
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website