The Buna River emerges at a rate of 43,000 litres per second from a limestone cliff beneath the Blagaj Tekija, a 16th-century Dervish house whose wooden lattice shutters frame the spring's mouth. Built circa 1520 by Ottoman architects who understood thermal engineering centuries before the term existed, the tekija served as a contemplative retreat for the Bektashi order until 1851, when Habsburg cartographers first mapped the spring's subterranean source. The karst aquifer feeding the Buna stretches sixty kilometres inland, surfacing here with water so cold it maintains 10°C year-round, a hydraulic fact that shaped monastic life for three centuries. Twenty-eight kilometres south, Počitelj clings to a north-facing escarpment above the Neretva River, its 1383 fortress and 1562 Hadži Alija Mosque forming a vertical townscape preserved by accidents of history. When the Ottoman Empire fortified the site as a strategic river crossing, masons laid streets at gradients approaching 40 degrees, engineering drainage channels beneath every staircase that still function after 441 years. The settlement lost military relevance after 1878 but gained UNESCO candidacy in 2007, its stone houses now hosting artisan workshops where blacksmiths demonstrate fire-welding techniques unchanged since the Bosnian medieval period. Kravice Waterfall spans 120 metres across the Trebižat River's tufa barrier, a travertine formation that grows three millimetres annually as calcium carbonate precipitates from the water. The cascade drops 28 metres into a natural amphitheatre where Neolithic pottery shards indicate human presence dating to 4,500 BCE. Unlike most European waterfalls, Kravice permits swimming in designated zones monitored by conservation staff, a privilege secured through a 10 EUR entry fee that funds riparian habitat restoration along the Trebižat corridor. Peak flow occurs in April and May when snowmelt from the Dinaric Alps triples the waterfall's volume, transforming the site from a summer swimming hole into a white-water spectacle visible from the canyon rim three hundred metres upstream. The Herzegovina day trip from Mostar to these three sites traces the Neretva valley's natural corridor, a route that connected Adriatic salt traders with Balkan hinterlands for two millennia. Modern tours follow the M17 highway, but the itinerary's logic predates asphalt—Blagaj controlled the river's headwaters, Počitelj guarded the middle crossing, and Kravice marked the western boundary where karst hydrology meets Mediterranean climate. Together, the loop demonstrates how geology dictated settlement patterns across Herzegovina, a principle visible in every spring, fortress, and waterfall along the route.