CINCINNATI -- Erik Keyster works in an old, round building that attracts a lot of visitors.

"People like to see things that are deadly, and people like to see things that are big, and people like to see things that are colorful," said Mr. Keyster, team leader of reptiles and amphibians at the Cincinnati Zoo & Botanical Garden.

So people trek into his workplace, the Reptile House, where they can see about 75 specimens, including Chinese alligators (deadly), green tree pythons (colorful), and a king cobra (big and deadly).

Here's what many visitors might not realize: The building itself is worth seeing too.

It has been on the zoo grounds since founder Andrew Erkenbrecher welcomed the first visitors in 1875.

Today it stands as the nation's oldest zoo building that has continuously housed animals, the zoo says. Which isn't so surprising, perhaps, given that Cincinnati has the country's second-oldest zoo, after Philadelphia's.

A renovation of the structure began this year thanks to a $408,886 matching grant from the National Park Service's Save America's Treasures program. The zoo is contributing an equal amount of privately raised dollars, bringing the total project cost to $817,772.

The building will remain open while crews do exterior work, including upgrades to the roof, mortar, windows and vents, as well as new gardens. That's to be done by June. The building will be closed for interior work next winter.

"It will be a gem, not just for lovers of animals and lovers of flowers and plant life, but also for lovers of architecture," said Martin Rahe, treasurer of the zoo board and a Cincinnati Preservation Association board member.

Victorian-era visitors knew it as the Monkey House. It was built 137 years ago for $14,000.The preservation association's executive director, Paul Muller, describes its style as "eclectic Moorish."

When the zoo was founded, "The reason they did these exotic styles of architecture is they were bringing the world to your neighborhood," Mr. Muller said. It only made sense that animals from around the globe would be housed in buildings with an international flavor.

Cincinnati architect James W. McLaughlin designed the gray limestone building, which has skylights encircling a dome at least 40 feet high. The interior is ringed by Corinthian columns, which at one time separated monkey cages along the inside walls.

Those stately columns might have been just an architectural warm-up for Mr. McLaughlin. He also designed the Cincinnati Art Museum, which opened in 1886.

Said Mr. Keyster: "Once in a while, while dusting off one of those decorative pillars in the lobby, you realize: They don't make buildings like this anymore."

According to a history of the zoo written by David Ehrlinger and published by the zoo in 1993, the Monkey House included several outdoor cages, including a bulbous one almost 30 feet tall.

Those cages are long gone. So, too, is the animal hospital that was part of a 1922 addition.

Monkeys moved out in 1951, and lizards, snakes, and tortoises became the building's residents. Its name was changed to the Reptile House.

The building survived a 1960 vote by the zoo board to raze it, according to Joy W. Kraft's The Cincinnati Zoo and Botanical Garden, a 2010 book in Arcadia Publishing's Images of America series.

In 1975 -- the zoo's centennial anniversary -- the Reptile House was placed on the National Register of Historic Places, along with the Elephant House and a former aviary that is now the Passenger Pigeon Memorial.

The renovation will give the building -- in particular the roof, which is now white -- a look that might seem new, but in fact is not.

"When we looked at historic photographs and paintings, the roof was actually red in the beginning," director Thane Maynard said.

So red it will be, which might draw more eyes to a building as worthy of attention as its residents.

First Published April 1, 2012, 4:29 a.m.