UKC

I'm considering a couple of days wandering around Pumlumon to take in a few Nuttalls and whatever else takes my fancy. I might start around Nant-y-moch and head up Afon Hengwm for starters.

A few practicalities: is there a good place to leave a car near Nant-y-moch dam? How is the going up the Hengwm; is it very boggy?

I'll be seeking al-fresco accommodation and wondering if Llyn Llygad Rheidol is quiet enough for that sort of thing. 

Otherwise I'd love to hear of any nice spots in the hills to visit; geological, archeological, morphological etc. also are any of the myriad lumps and bumps in the area especially good view wise?

It's stunning backpacking country! And usually very quiet, esp compared with Bannau Brycheiniog and Eryri. I did a fab 3 dayer from Machynlleth to near Borth with friends a few years ago and top locations on route were Glaslyn on Glyndwr's Way to the north east of Pumlumon, and Llyn Craigypistyll and the track down to the Leri Valley.

Along the tops of course you can drop down to the sources of the Severn and the Wye.

There is parking at Nant y Moch reservoir dam and people stop off there with campers. We did our trip by public transport, but I'd have no concerns about leaving a car there for a couple of days. If concerned, park at Eisteddfa Guirig on the A44 for a fee for parking at the farm.

I haven't camped at the llyn, I've only actually been to that spot once, on a major incident for a bunch of lost and hypothermic students in utterly vile weather! There is a vehicle track to it though it's gated, and the llyn is dammed. We camped in the upper Hengwm valley. And yes, the valley itself is, like most of mid Wales, more than a tad boggy and soggy! But a great area, have fun!

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There's a big car park at the dam (quiet enough, but not sure I'd leave a car there for multi day) and some parking up the road towards Maesnant. The north side of the Hengwm is a lot drier (relatively!) going than the south and once you're past the bit chewed up by trail bikes, is OK once you pick up the path which is further up the bank than you think. Getting back across the river to go up Cwm Gwerin can be a bit tricky to find a crossing spot. If you go right up to the top end of the valley where the Land Rover track to Bugeilyn starts, you can splosh through a boggy bit (the stream is in a culvert at that point) and work your way up to Carnfach Bugeilyn and back along the ridge to Pumlumon, which is nice. Cwm Gwerin would be my choice to camp up there - a bit less foreboding than Llygad Rheidol and some interesting craglets and bits of geology to look at. Look out for the Buwch wen a llo (white cow and calf) up on the south side of the Hengwm valley - a couple of big quartz boulders that would have been welcome waymarks in the fog. Once you're out of the valleys, it's relatively dry, though it has been chucking it down for the last couple of days.

A wander up to Carn Gwilym and a look over Cwm Hyddgen where the Glyndwr battle was back in the 1400's (https://en.wikipedia.org/wiki/Battle_of_Mynydd_Hyddgen) is a good easier day - various loops back from there to Maesnant - the footbridges across the three rivers running in to the top of Nant y Moch marked on the OS map are actually there. Glaslyn and Foel Fadian are nice.

If you've got a really bad list ticking itch, then search for "Y Pellenig" - a list of the remotest hills in Wales, several of which are around there. If you fancy a bit of background reading, "Good men and true" by Erwyd Howells records the stories of the shepherds and villagers that lived in Nant y Moch before it was flooded. There's a black and white film online (British Pathe, I think) of the last days of the valley community, which is worth a watch to see what's under the reservoir.

If you feel like splashing out, Banc Llechwedd Mawr AirBNB would make an amazing base camp for exploring round there (https://www.airbnb.co.uk/rooms/1049247718770858595?source_impression_id=p3_...) About as dark skies as you can get in southern Britain.

Have fun!

I don't think I can contribute much considering the replies above, but it's a fantastic area. Unlike Deri, I favour the south side of Hengwm because I find the ruined house of Hengwm-annedd to be an evocative spot, particularly in spring when daffodils are in flower there.
https://www.geograph.org.uk/photo/2394932

But yes, the going is damp and rough underfoot. I second the suggestion of Cwm Gwerin with the big rock "arch" of Craig y March being an interesting feature. Good description here:
https://www.ukclimbing.com/logbook/crags/craig_y_march-19721/#overview

Glaslyn is well worth a visit if you like bleak and windswept lakes and nearby Tarren Bwlch-gwyn always looks enticing on the map but I've never wandered that way. 

Hi Mike - Tarren Bwlch gwyn is worth a poke about - unfortunately the two waterfalls there have been curtailed when they dammed the outfall from Llyn Bugeilyn/Cwmbyr  and changed it so all the water from that bit now runs down to Nant y moch (hence the random concrete culverts you come across). There's the old leat that fed the lead mine at Cwmbyr that you can pick up and follow across the scarp - apparently you used to be able to walk behind Rhaeadr Ddu, though I chickened out of scrambling across some very wet and mossy rocks. Must have been a bleak place to be working in the mines up there! 

Heaps of industrial archaeology around there if that's your bag - I've never got round to visiting the Silver mountain museum in Llywernog but it's supposed to be pretty good.

Thanks to all respondents. Plenty of food for thought there. I might stick to a high level route as I fancy a change from Cambrian bog hopping.

But good tips on camping spots to descend to.

Our two camping spots on our trip: on a tributary of the Hengwm at the top end of the valley, and the at the abandoned farmstead at Bwlchystyllen, with Craig y Pistyll in the background. The Welsh Tourist Board had a series of adverts on Wales: The Big Country a few years ago, and this part of the country certainly is - big, and empty.

I'd never twigged that the water flows the other way but you can follow the path of what I assume is a pipe/culvert on the aerial photography. Never twigged about that leat either, though it's visible on the photos too now I look. Funny the OS map doesn't show it.

I was at Silver Mountain earlier this year. A surprisingly entertaining day for my 5yo son (and I enjoyed it too).

Someone from the hydropower place gets the job of going up and strimming along the top of the culverts that run out from llyn Bugeilyn to join the southern Hengwm - that's how I noticed them. There's another load picking up the water that should be going to Pistyll y llyn and turning it back to llyn Penrhaeadr and Anglers retreat and so to Nant y Moch. Just a newer generation of the miners leats, I suppose. They had ones running east and west from the mine at Cwmbyr picking up the streams falling off the north edge of the plateau - when I first moved here you could see the line of the western one as it picked up the falls in the northern Hengwm - the trees have obscured it now. The latest generation is a micro hydro running off the drop from the plateau to the northern Hengwm - generations of getting water to go where you want!