The owners of a historic La Cañada Flintridge estate with a near-amusement park in the backyard have accepted an offer from an unidentified buyer just four days after listing the property for $8.5 million.

“As soon as we hit the market, their agent called, and I had an offer from them right away,” said Kathy Seuylemezian of Coldwell Banker Realty, the listing agent, by phone. “It was a quick escrow and all contingencies have been removed, so the chance of it falling out is slim to none.”

The 5,622-square-foot Dutch Colonial Revival-style residence, built in 1915 and designated a historic property by the city, features a total of six bedrooms and eight bathrooms between the main and guest houses. It sits on over 1.5 acres of manicured grounds with a unique feature — a kiddie train.

Current owners David and Sherry Kirchheimer discovered rusted remnants of train tracks that a past owner had installed, they told the Wall Street Journal, which first reported the story. Records show the couple bought the house in July 2008 for $6.175 million.

The Kirchheimers recreated the railroad with the help of late Disney Imagineer Bill Tyson in 2011.

Today, the Flintheim Railroad features a train station with a crossing light. The kid-sized train for up to five people travels on roughly 530 feet of tracks through a tunnel, over two bridges and past a general store and a mining camp. The train shed is a replica of Disney animator Ward Kimball’s Grizzly Flats Railroad, which operated from the backyard of his San Gabriel home between 1942 and 2006.

A winner of multiple “La Cañada Beautiful” awards, the grounds include a 50-by-19-foot pool with a diving board ringed by a two-level deck, a rose garden and a wisteria-topped pergola.

The custom play structure has rock-climbing walls and a bridge.

A fenced-in, irrigated vegetable garden, fruit trees and a built-in barbecue island with bar seating enhance the bucolic setting centered around the 5-bedroom main house, which features a covered front porch overlooking the manicured lawn.

The house, which has been renovated over the decades, opens into a grand foyer with a curved staircase.

French doors flood the formal dining room with natural light and a fireplace anchors the living room.

The gourmet kitchen features top-of-the-line appliances, a large island with a prep sink, a deep pantry, a separate butler’s pantry and a breakfast nook. It flows into the large family room with a fireplace.

A second staircase off the kitchen leads to an office, two bedrooms and the primary suite, which has direct access to a balcony.

The suite also features a sitting room warmed by a fireplace, a raised bedroom, two deep closets and a spa-inspired bathroom with a jetted tub, double sinks and a separate shower stall.

Other structures on the property include the one-bedroom guest house with a living room and full kitchen, a fitness space with a balcony above the separate two-car garage and a dedicated workshop and storeroom with a woodworking bench. The game house boasts a stone fireplace, bar area and pool table.

There’s a large enclosed play area for dogs.

The property has a Generac 20-kilowatt generator with a backup propane tank, a San Marino security system and Ring cameras. In addition to the garage, there’s a two-car carport and a flat, circular driveway that can accommodate a dozen vehicles.

Seuylemezian anticipates the sale will close within two weeks, though the sale price has not yet been disclosed.