Homer Tunnel is a historic engineering marvel that pierces through the Darran Mountains at 945 meters elevation, linking Te Anau to Milford Sound. Construction began in 1935 with just five men using picks and wheelbarrows during the Depression, taking 19 years to complete! The tunnel stretches 1.2 km with a dramatic 10% gradient, creating an exhilarating driving experience through the darkness. Workers lost their lives to avalanches during construction - a memorial honors them. Traffic lights control one-way flow during peak season due to avalanche risk at the portals.