Bugsy was the last cat remaining at the sanctuary. (CBC)

The long-standing cat sanctuary on Parliament Hill has officially closed down.

The popular tourist destination was once home to dozens of stray cats living behind the Parliament buildings. They were used to catch mice, but by the 1950s, they weren't needed anymore.

Since then, the population dwindled down to just four.

Three of the cats were recently adopted by volunteers. Just one cat, named Bugsy, is still roaming the Hill.

Decades-long volunteer to adopt final stray

Brian Caines spent the last 20 years taking care of the strays, and he'll be bringing Bugsy to his home.

"He's quite observant," Caines said of Bugsy, a male that's been living at the sanctuary for about five years.

"Whether he can really observe what's going on, I'm not sure, but he distrusts me now because he knows that I'm the bad guy. So I can't catch him. We've been able to get the other ones but I just can't catch him."

Caines has already adopted three cats from the Hill, with the latest caught last Saturday.

Once Bugsy is caught, Caines said the miniature wooden buildings that house the cats will be torn down.

"I say that I'm very sad, but I'm not upset. It's been a really big part of my life," Caines said. "I've also met wonderful people … and we've developed a wonderful friendship and it will continue. The reason we developed the friendship will be gone, but we all have cats from the Hill. All of the volunteers have a cat from the Hill."