Indianapolis Zoo officials are hoping to finish strong on the organization's largest fundraising effort since the zoo moved to White River State Park in 1988.

They've raised $25 million of the $30 million goal for the second phase of a capital campaign that began about two years ago. The effort, dubbed The Campaign for Conservation and Community: Saving the Orangutans, will pay for the construction of a new International Orangutan Center, along with improvements to the zoo's entry pavilion, tiger exhibit and Flights of Fancy bird exhibit.

"We're exactly on target for where we predicted we'd be," said Karen Burns, the zoo's vice president of external relations and fundraising chief.

She said 158 donors have pitched in so far, including large gifts from the Dean & Barbara White Family Foundation and Lilly Endowment. The first phase of the Campaign for Conservation and Community kicked off in 2002 and raised $31 million, Burns said.

The zoo moved to White River State Park in 1988 after raising $60 million from donors. The zoo does not receive taxpayer support.

Indiana Gov. Mitch Daniels and Indianapolis Mayor Greg Ballard joined zoo officials Tuesday to break ground on the $21.5 million orangutan center, which Burns described as the "most significan single exhibit" for the zoo since its founding in 1964.

The center will provide a state-of-the-art home to eight of the world’s most endangered primates, while offering human visitors a unique perspective. It's scheduled to open in May 2014.

"This is truly unlike anything we've done or anyone else has done for that matter," Burns said shortly before the 11 a.m. groundbreaking.

The zoo said in August it received a $2 million gift from the family foundation of Dean and Barbara White of Crown Point. Dean White is co-founder of Merrillville-based White Lodging, whose developments include the towering JW Marriott Hotel that overlooks the zoo in downtown Indianapolis.

Architectural highlights of the orangutan center include the 150-foot tall Beacon of Hope that will be illuminated at night and a 90-foot-tall, four-season atrium featuring both indoor and outdoor viewing for visitors.

Also, the Hutan Trail mimics an orangutan highway through the forest and allows the animals to leave the atrium and travel to different places throughout the zoo, above ground. An aerial cable ride complements the trail by giving visitors a unique view of the orangutans.