The team, which included local Korean firms Ga-One Landscape Design and Group Han Associates, won the competition for a concept design and feasibility study for the 560ha park.
Although AECOM Design & Planning's New York office was leading the proposals, UK-based director Jason Prior, who formulated the masterplan for the Olympic Park, was one of the key design advisers.
The winning entry — Gaia: The Living World — aimed to revitalise the urban realm and showcase Korean heritage.
The proposal opened the entire lake front for community use, reconnecting the city to the waterfront.
It also proposed new attractions, including a night safari at the Great Savanna attraction, Korean Forest, and a winter garden complete with a giant waterfall.
Consultancy EDAW, which merged with AECOM in 2005 and changed its name to AECOM Design & Planning last year, developed the original theme park plan in the 1980s.