Castell Harlech

Gwent Castles 09

Original uploader Owain at English Wikipedia., CC BY-SA 2.5 <https://creativecommons.org/licenses/by-sa/2.5>, via Wikimedia Commons

Newport/Casnewydd

There are other Gwent Castles we could mention (Goodrich and Caldicot come to mind) but we'll finish with the first castle I ever saw. I grew up in Cwmbran but my parents were from Newport and we would often be there. I used to love to see the castle. To me it was like a time travel machine that had come from another age and parked itself plonk in the middle of everything. In those days you couldn't explore it and that probably added to the mystery and attractiveness of what I once read of as being "The finest preserved Norman gateway in Wales".

Gwent Castles 08

Castell glas/Green Castle

I think this all but disappeared castle near the Ebbw River is the one connected to Ebbw house in school but I may be wrong. More here.

Gwent Castles 07

Tyssil, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Caerleon
In school this house was called Isca - short for Isca Silurum, the Roman name for Caerleon (preserved in the name Risca - Yr Isca). This saved confusion with C for Chepstow.
(More here and here)

Gwent Castles 06

Pauline Eccles, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Monmouth/Mynwy

(More here)

Gwent Castles 05

Bob McCaffrey from Rickmansworth, UK, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Raglan (See here)

Gwent Castles 04

Nilfanion, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Chepstow/Casgwent
(more here)

Gwent Castles 03

Pauline Eccles, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Usk Castle/Castell Bryn Buga

(More here)

Gwent Castles 02

Cadw, OGL v1.0OGL v1.0, via Wikimedia Commons

White Castle/Castell Gwyn

I must confess I don't recall ever seeing White Castle (Castell Gwyn).

It's somewhere up Abergavenny way. Looks quite good. 
More here

Gwent Castles 01

Davidmholmes51, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Skenfrith

What set me off on this was that someone mentioned how Wales is full of castles. I then remembered that in school our houses were named after castles in Gwent. What happened was that the Grammar School I passed for had four houses named after Gwent rivers and the Secondary School it merged with had four houses named after Gwent castles. After the merger, it became eight houses all named after Gwent castles but retaining some connection with the original river names (which must have been Ebbw, Monnow, Severn and Usk or was it Wye?). Ebbw and Usk Castles exist but there is no Monnow, Severn or Wye Castle so they were renamed after Skenfrith (Ynysgynwraidd), Monmouth and White (was it?). I was in Skenfrith - inevitably tagged "Scumfilth" by members of other houses. Skenfrith is a bit off the beaten track and there's not much to look at but I did manage to drag my parents off there one day to at least see it. it looks more impressive in the picture than I remember it all those years ago. (More here).