The Brecon Beacons National Park has the lowest profile of Wales’s three national parks, but it is nonetheless the destination of thousands of walkers. Rounded, spongy hills of grass and rock tumble and climb around river valleys that lie between sandstone and limestone uplands, peppered with glass-like lakes and villages that seem to have been hewn from one rock. The park straddles three Welsh counties: Carmarthenshire, Powys and Monmouthshire, covering 520 square miles. Most remote is the far western side, where the vast, open terrain of the Black Mountain (singular) is punctuated by craggy peaks and hidden upland lakes. The southern flanks bare bony limestone ribs, beneath which are the chasms of the Dan-yr-ogof caves. East of this wilderness Fforest Fawr forms miles of tufted moorland tumbling down to a rocky terrain of rivers, deep caves and spluttering waterfalls around the village of Ystradfellte. The heart of the national park comprises the Brecon Beacons themselves, a pair of 2900ft hills and their satellites. East of Brecon, the Black Mountains (plural – not to be confused with Black Mountain) stretch over the English border, and offer the region’s most varied scenery, from rolling upland wilderness to the gentler Vale of Ewyas. The Monmouthshire and Brecon Canal defines the eastern limit of the Beacons and forges a passage along the Usk Valley between them and the Black Mountains. This is where you’re likely to end up staying, in towns such as the county seat of Brecon, the charming village of Crickhowell, or sprightly Abergavenny, nestled below the Black Mountains.