An open house is scheduled for 3:30 p.m. to 5 p.m. CST Tuesday.
The park says Phase I cost $6 million, provided from park fees, and included demolition of the administrative building to make way for a large lobby, information desk, ticket sales and restrooms.
Phase II cost $10.4 million and was paid for through the American Recovery and Reinvestment Act of 2009. The rest of the old building was stripped down then rebuilt for exhibits, office space and book sales.
The work was done under Leadership in Energy and Environmental Design guidelines, with officials hoping the finished project will receive gold-level certification as a sustainable, "green" building.