The mystery of the missing sea is one that has personally intrigued me recently. Through all of the Welsh history I have covered on this channel, I have never encountered a phenomenon as mysterious as what I've dubbed as the "islands that aren't islands".
Throughout a small valley in Wales, near the towns of Porthmadog and Tremadog, there are 10 hills that aren't called hills at all, but "islands", despite being completely away from the ocean, a phenomenon that is completely unique throughout the history of Wales.
Wales' history is full of mysteries, and these islands that aren't islands, surrounded by a missing medieval sea, is another one of them.

Chapters:
0:00 Islands that Aren't Islands
0:45 Ynys, Ynys, Ynys
2:52 Traeth Mawr
5:10 How to Remove 13 Miles of Coastline (100% Effective!)
7:35 William Madocks

Sources (turn on captions):
Hislop, M. (2024). A Guide to the Medieval Castles of England. Pen & Sword History,
[1] pp. 175,
[2] 176.

Llyfrgell Genedlaethol Cymru / National Library of Wales. Cambriae Typus.
[3] https://www.library.wales/discoverle....

Rhind, P.M. and Jones, A. (1994). Brackish saltmarsh communities in the Glaslyn marsh trust reserve. Field Studies, 8,
[4] p. 373.

Robinson, G. and King, T.J. (2019). At Home on the Waves: Human Habitation of the Sea from the Mesolithic to Today. Berghahn Books,
[5] pp. 145146,
[6] 146,
[7] 146148,
[8] 147.

Thomas, D., (1959). MADOCKS, WILLIAM ALEXANDER (1773 1828), industrialist and philanthropist. Dictionary of Welsh Biography.
[9] https://biography.wales/article/sMAD...

Tweet by @KeithAPettit:
[10]   / 1742951095784071278  



Maps:
© OpenStreetMap contributors, licensed under CC BYSA: https://www.openstreetmap.org/copyright
https://www.floodmap.net/



Music courtesy of the YouTube Audio Library:
Rain Cloud Music Emily A. Sprague
Sunrise Over Big Data Country Dan Bodan
A Slow Dream Emily A. Sprague
Stuck In The Air The Tower of Light
Ammil The Tides



Images of, and from:
Afon Glaslyn and Traeth Mawr by Bill Boaden, CC BYSA 2.0 https://creativecommons.org/licenses/..., via Wikimedia Commons
A sea of grass, southwest of Tremadog by Christine Johnstone, CC BYSA 2.0, via Wikimedia Commons
Cnicht From the Cob, Porthmadog, Gwynedd by Peter Trimming, CC BYSA 2.0, via Wikimedia Commons
"Island" near Farmyard by Dewi, CC BYSA 2.0, via Wikimedia Commons
Y Cob, Porthmadog o'r awyr, Gwynedd, Cymru (Wales) by Llywelyn2000, CC BYSA 4.0 https://creativecommons.org/licenses/..., via Wikimedia Commons

all other images are public domain, via the Yale Center for British Art, the British Library, and the National Library of Wales

#wales