BOSTON (AP) -- A dozen giant bronze animal heads representing the signs of the Chinese zodiac are stopping people in their tracks in downtown Boston and sparking conversations.

“Circle of Animals/Zodiac Heads,” by contemporary Chinese artist and human rights activist Ai Weiwei, is the latest in a series of outdoor public art projects on the Rose Kennedy Greenway intended to delight, awe and educate the thousands of tourists and workers who walk through the park daily.

“The goal of all public art is to engage people,” said Lucas Cowan, the public art curator of the Greenway Conservancy, which oversees the 2.41-kilometer long ribbon of open space that was once a dim, grimy place in the shadow of an overhead highway.

“To be able to bring people here where they see them up close and not in a museum is very important,” he said. “If people just walk past this, then we’ve failed.”

The 3-meter-tall cast bronze sculptures, which weigh 1,600 to 2,100 pounds apiece when the stem and base are included, are arranged in an outward-facing circle surrounding a popular children’s splash area called the Rings Fountain. They are positioned in order -- rat, ox, tiger, rabbit, dragon, snake, horse, goat, monkey, rooster, dog and pig.

They are based on similar but smaller zodiac sculptures that once adorned the fountain clock in the European-style garden at the Yuanming Yuan, an imperial summer palace outside Beijing.

The palace was ransacked by British and French troops in 1860, and the heads stolen. Most have been recovered and returned to China, but two remain missing, Cowan said.

“By enlarging them like this, the artist is saying, ‘They belong to us; give them back,’” he said.

Cowan also hopes people who see the sculptures educate themselves about the social justice and political issues the artist is involved in. Ai this year has been drawing attention to the European refugee crisis.

The Boston installation, which will be in place until October, is part of a world tour of the animal heads owned by a private collector that started in 2010 and has already visited several U.S. and international cities.

Even as workers put the finishing touches on the exhibit earlier last week, dozens of people stopped to take pictures or just gaze up at the detailed sculptures.

“We live just down the street, and we knew they were putting them in, but when we saw them, we just said, ‘Wow,’” said Davida Carvin, who was checking out the sculptures with her friend, neighbor and walking partner, Andrea Mattisen-Haskins. “I’ve seen a lot of art along the Greenway, and this is right up there with the best.”

“The quality is spectacular and the detail and texture is amazing,” said Mattisen-Haskins, as the pair snapped pictures.

Howard Wu, a Bishop, California, resident visiting Boston for the first time, stumbled upon the animal heads on his way to the nearby New England Aquarium and was astonished.

Wu, who is half Chinese, immediately recognized them as the Chinese zodiac and understood their cultural significance.

“They are just exceptional,” he said as he snapped dozens of pictures. “They will bring Boston good luck.”