Proposals have been put forward for a tunnel link in Bulgaria that would be Europe’s longest. The 37km long twin tube tunnel would form part of Bulgaria’s Struma Highway, which runs 150km from Dakalovo to the Greek border. The tunnel option has been proposed largely due to environmental reasons. The route of the highway takes it through the area of the Kresna Gorge but on both environmental and technical grounds, building the road on the surface is out of the question and the best solution is to construct a