Southwest of the village, where the Afon Senni runs into the Usk, the ruin of Castell Du stands over the river crossing. A stretch of wall about 26 metres long survives, along with a D-shaped tower up to six metres high. Two WWII pillboxes were built on the site and faced with masonry to mimic castle walling. Cadw suggests the castle may have been raised by Llywelyn ap Gruffudd around 1262, and may be the "new castle beyond Brecon" that the future Edward I destroyed in 1265, though little about it is certain.
The village itself sits along the A40, nine miles west of Brecon, on the corridor between the Senni valley to the south and the plateau of Mynydd Epynt to the north. The core is a run of older terraces with newer estates behind; adjoining Defynnog, a little way south, is older and more stone-built.
There are four pubs. The Usk & Railway Inn was built in 1870 as the Railway Inn, to serve the station that once stood at Devynock & Sennybridge, and it has stayed an inn ever since. It has a bar, a separate dining room and six en-suite rooms, usually three changing ales, and a garden. The kitchen lists truffled creamy garlic wild mushrooms on sourdough, Gower Gold beer-battered cod, a miso butterbean cassoulet with spiced hispi cabbage, steak-and-ale pie, a classic beef burger, and a homemade curry in meat or vegetable form. Dogs are welcome in the bar on a lead, though not in the dining room.
The Abercamlais Arms and the Red Lion sit on the High Street. The Abercamlais does British pub food and takes dogs; the Red Lion is the smaller, traditional local, with Felinfoel Double Dragon and Dragon Welsh IPA on cask. On the A40, the White House has reopened under new management, running its bar, bar food and Sunday lunch, with a garden, countryside views and a large car park; bedrooms and a full dining room are still to come. Its own description of what it is doing is "simple things, done properly."
For provisions there is the Londis at the Glanusk service station, and a café at the livestock market. Three miles out at Pentre-bach, the community-owned Shoemakers Arms has a garden, changing cask beer and views towards the Beacons and Epynt.
South of the village, at Defynnog, the Grade I church of St Cynog is the parish church, most of it late fifteenth century on a site recorded in 1254. In the porch is an inscribed stone from the fifth or sixth century, cut later with two crosses. The font carries the names "Siwurd + Gwlmer", traditionally described as Wales's only Runic inscription, though disputed. The National Park calls the church "striking within the valley landscape, forming an iconic and picturesque view."
The walking here is serious country. The Epynt Way is a 90-kilometre permissive circuit around the boundary of the Sennybridge training area, and the waymarked Disgwylfa trails climb north from the conservation centre onto Epynt grassland, over ground worked by red kites, merlins and curlew. Both cross military land: fog forms fast, range signs mean what they say, and the impact area is never to be entered. The T6 bus stops at the Post Office seven days a week and runs east to Brecon and south past the Dan-yr-Ogof showcaves; the nearest railway station is twelve miles west at Llandovery.
The Devynock Agricultural Society held its first show at Trecastle in September 1865. The Sennybridge Show still fills a summer field with cattle, sheep, horses, baking and vintage machinery, much as it has through two world wars, economic changes and the pandemic.