Katya, who is now 36 years old, is one of several former circus animals being kept inside the smelly bus and a nearby minivan.
For years she was part of the St Petersburg State Circus, where she was one of the bears who rode a motorcylce around a ring. During the Olympics she performed at a ceremony marking the opening of the football competition, and since then she appeared in two movies.
She is now one of the animals caged inside the painted bus in which she once travelled with the circus. The bus has been sitting in a car park near a busy road since 2009.
"They can't move normally and start going crazy," The Guardian
quoted Zoya Afanasyeva, of the animal rights group Vita, as saying.
"Apparently they are being taken care of, but not more often than once a day, and this care is perfunctory because the smell here in the parking lot is unbearable."
Katya now spends much of her time jumping up and down, and biting at the rusty metal railings with her chipped teeth. Nearby are birds with atrophied muscles and cats with pus-covered eyes.
Some of the animals are occasionally removed from their cages to have their pictures taken with children and tourists.
Circus director Viktor Savrasov said the animals are cared for and Natalya Arkhipova, who was Katya's trainer and is now retired, visits the bear. He added that the animal's fate could have been worse, as her former trainer could have had her put down.
Animal welfare groups, and concerned individuals, have spoken out against the use of wild animals in circuses for years. There has been concern about training methods and the lives the animals lead.
"Bears, elephants, tigers, and other animals do not voluntarily ride bicycles, stand on their heads, balance on balls, or jump through rings of fire. They don't perform these and other difficult tricks because they want to; they perform them because they're afraid of what will happen if they don't," states PETA.
Constant confinement leads to stress and behaviours such as swaying, pacing, bar-biting and self-mutilation.
Animals end up in various places once they are no longer of use to a circus.
"Larger circuses may sell unwanted or old animals to smaller enterprises or to private zoos. Primates, especially chimpanzees may end up the victims of laboratory experimentation," states Animal Liberation Queensland.
"Investigators in the US believe that former circus animals there have been bought by game ranchers (where they are easy targets for trophy hunters), and by suppliers to exotic food restaurants."
One of the organisations working to try to improve animal welfare in Russia is Vita