The Sveti Ilija Tunnel bores straight through the Biokovo massif, connecting the coastal towns of the Makarska Riviera with the Imotski hinterland behind the mountain. At 3.8 kilometres, it is one of the longer road tunnels in Croatia, and its opening transformed what had been an isolated stretch of coast into a practical route for inland travel.
For travellers, the tunnel matters mainly as access to the extraordinary Imotski lakes — the Blue Lake and Red Lake — which lie in sinkholes of such scale and colour that they look entirely improbable. The drive through takes only a few minutes, emerging into a completely different landscape of limestone valleys and traditional stone villages.