The city of Roanoke has pledged $500,000 to help improve Mill Mountain Zoo, city and zoo officials announced Monday.

The hefty grant, the biggest in zoo history, would be given over three years in $166,000 increments, City Manager Darlene Burcham said, and is linked to the zoo raising matching funds from other sources.

The gift was announced in a short mountaintop ceremony Monday morning, amid the hoots and cries of birds and animals.

"We believe that great things are happening here at Mill Mountain Zoo," Mayor Nelson Harris said. "It is one of the great cultural assets that we have. We hope this will energize others to step up to the plate."

The zoo's executive director, Sean Greene, called the city's gift "by far the largest contribution that the zoo has ever seen." With the match, the total would exceed the $900,000 zoo officials told the city in October it would need for capital improvements such as fixing aging exhibits and building a new quarantine facility.

The announcement comes on the heels of a zoo fundraiser March 8 starring former Columbus Zoo director and television personality Jack Hanna that raised about $250,000 for the zoo. Some of that money could qualify as matching funds for the city's grant, Greene said.

He said the zoo will contact supporters in an effort to drum up the rest of the challenge money.

The city grant could be applied to any number of current and upcoming zoo projects, including a new Virginia wildlife exhibit, an African penguin exhibit and the quarantine area. The zoo is seeking to improve its financial stability and upgrade existing exhibits prior to an accreditation inspection this summer. The zoo is accredited by the Association of Zoos and Aquariums, but must make some improvements in order to remain so, Greene said. The association granted the zoo a year's extension to make the adjustments necessary for maintaining accreditation.

The zoo also is raising money for an endowment to help fund future operations.

"We need to raise at least $3 [million] to $4 million just for the projects we have on tap," said Sara Brooks, zoo board president.

The zoo atop Mill Mountain has an annual budget of about $700,000, which is funded largely by gate admissions, programs and private donations. About 10 percent of its money comes from government sources.

The zoo has gone through highly publicized trials in recent months with the death of zoo icon Ruby the tiger and the infamous escape of Oops the monkey. But in part because of the new infusion of funds, the zoo is stronger now than it has been in some time, Greene said Monday.

"We're in a lot better shape than we were several years ago," he said.