"The sun is coming up," LaBonge told him. "We live to see another day!"

Shankman smiled and stepped onto a trail across from the Greek Theatre.

"I'll tell you something you're allowed to say when you're my age," he said with a shrug. "It's good for the ego. It really is."

He was never an athlete. "I might have been what you call a 'nerd' today," he said.

Shankman earned his doctorate in physical chemistry at the University of Toronto after studying the vapor pressure of sulfuric gas solutions. With his wife, Elizabeth Stern Shankman, a pathologist whom he'd met at college in 1935, he moved to Los Angeles after school and started working for a vitamin company.

His bosses asked him to design a pill that would stop gray hair. He tried -- but in the process stumbled upon a bacterial medium that helped speed up scientists' ability to isolate proteins and other material. In 1944, he hung his own shingle -- Shankman Labs, where he analyzed everything from pharmaceuticals to Army rations.

Along the way, he discovered Griffith Park, 4,467 acres of scrub oak and chaparral -- and more than 50 miles of trails. "I was in love with it from the first day," he said.

In 1976, after he began suffering from angina, friends suggested he start hiking.

"At first, it was principally therapeutic," he said. "But I just kept on walking."

After his wife passed away in 1980, around the same time that he sold his business, he decided that he needed a project. He walked from Tijuana to San Francisco over seven years, all in tiny increments of three or four miles at a time. Later, he founded a group of walkers dedicated to the steep staircases that zigzag across eastern portions of the metropolis, particularly in Echo Park and Silver Lake.

But, mostly, he stuck to the park up the street, the park that would sustain him, the park that he says is the city's "lungs."

He has walked through driving rain -- indeed, he has been known to stoop down and kiss the ground at the onset of the rainy season -- and has twice broken ribs in nasty falls, walking the next day in both instances.

He's become picky about his walking partners -- a right of age, perhaps.

He hates to walk alone but, on the other hand, "you find out how boring some people can be if you walk with them every day," he said. "And I include myself in that."

Most days, he walks with his companion, 81-year-old Anneliese Clay, whom he met after she moved into her daughter's house in his neighborhood seven years ago. They spend their time talking about European history, doting on woodpeckers and other critters, bickering over the identifications of unusual plants they stumble across.

"Sol understands that you need nature, that you need to walk -- that it improves your spirit," Clay said. "He lives what he says. That is his principle."

In August, LaBonge -- who became close with Shankman after the park's terrible 2007 wildfire chased Shankman off his regular trail -- and several other lovers of the park dedicated a little red bench to Shankman.

"He's an inspiration," LaBonge said.

The bench is on Riverside Trail, east of the Greek Theatre and not far from Cedar Grove. It's easy to find; they put it under a formidable live oak, the only shade tree for several hundred yards in any direction.

"It's not Shangri-La," Shankman said. "But with a little shade, it's a nice spot."

If you get there early enough, you might see Shankman coming around the bend, the rotunda of the Observatory rising over his head, an orange in his pocket, stabbing the agave walking stick he plucked from a neighbor's rubbish pile into the dirt with every other step. "It's nice when you see people above you, up on the slopes, when the sun is rising right behind them," he said. "Everybody looks like a saint."

scott.gold@latimes.com