The popular Milford Track was mostly sold out within half an hour of bookings opening today, with thousands queuing online to secure a spot. There were about 7000 available for the 'Great Walk'. The Department of Conservation (Doc) opened up its booking system for its Great Walks yesterday, when the Paparoa Track was the first one up for bidding. The Milford Track was next for booking and opened at 9.30am today. Doc heritage and visitors director Cat Wilson said demand was intense from the moment bookings opened, with about 13,500 users already in line - higher than the roughly 12,000 users recorded last year. "The Milford Track remains one of New Zealand's most sought-after experiences, and we saw extraordinary demand again this morning," Wilson said. "Despite the very high traffic volumes, the booking platform performed well and people moved steadily through the queue." The Paparoa Track also proved popular, attracting more than 4000 in the online queue when bookings opened yesterday morning.…