Henderson, a 23-year-old Ohio State University student, sneaks into utility tunnels, abandoned prisons and derelict hotels for the thrill of it.

He chronicles his adventures at www.forgottenohio.com.

The Web site caught the attention of a Chicago publishing company that was planning a book series on the types of buildings Henderson likes to explore.

"They came to me," said Henderson, an English major. "I was really flattered. I'm still in college, you know."

The book, Forgotten Columbus (Arcadia, $19.99), offers a pictorial history of landmark buildings, some long since demolished.

Although it doesn't concern his illegal hobby, the volume does feature several photographs that he -- or fellow explorers -- snapped during excursions.

The rest of the photos are from the Columbus Metropolitan Library collection.

Henderson has prowled old buildings for several years.

The practice is something of a national trend, called "urban exploration" (or "infiltration") by its adherents. It's also illegal and dangerous: Henderson admits having had close calls with falling bricks and rotting floors.

He finally stopped sneaking into an abandoned prison in Roseville after becoming ill all three times he entered.

"Never again -- it's a scary place," he said.

Henderson has never been caught.

"Never been arrested, never even came close. But I'm really, really cautious. I get made fun of for being so cautious."

The honorable urban explorer has a code of conduct: Don't vandalize, don't steal from and, any more than necessary, don't disturb a site.

The book pictures many buildings that, were they still standing, an explorer would no doubt love to infiltrate.

The cover features the mammoth Central Ohio Lunatic Asylum, later called the Central Ohio Psychiatric Hospital.

Often billed as the largest building in the world under one roof, the institution for the mentally ill was demolished in the 1990s.

Also long gone are most vestiges of the empire of Dr. Samuel Brubaker Hartman.

The doctor -- who made a fortune selling Peruna, a patent medicine that was 28 percent alcohol -- built a hotel, plants and a theater Downtown.

His Hartman Farm south of Columbus was a sprawling beef and dairy operation that Henderson speculates may have contributed to the nickname "Cowtown."

Among surviving landmarks, the long-empty Seneca Hotel, recently purchased for redevelopment, is a Henderson favorite.

"I've been inside three times," he writes on his Web site.

He encountered several homeless people, including one smoking crack, in the E. Broad Street building.

"No one tried to kill us or anything, but it's still most definitely not advisable to go by yourself."

His book also examines the old Ohio Penitentiary, the Fort Hayes complex and several OSU buildings.

Henderson hopes to do books on Cleveland and Cincinnati.

He also is eyeing an empty missile silo in Colorado that he'd like to explore.