This Montreal home for sale features a sleek glass cube atop a 110-year-old duplex (PHOTOS)

Walking past this old house in the heart of Outremont, you might notice a glass cube peeking out from atop the roof. It's easy to miss, but a total showstopper for anyone who spots it — an unusual crowning detail for a residential property.

"What is that modern box doing sitting on top of that traditional, brick building?" you might wonder. Since the home is for sale, we can not only answer that question but also allow you to peek inside. And spoiler alert: the glass cube is not a swimming pool or a sunroom or a library, it's a whole damn penthouse spanning 1,600 square feet.

The current owners built the addition in 2018, turning a 110-year-old duplex circa 1908 into a luxury fourplex. It's a true meeting of past and present (or even future considering its minimalist, cutting-edge design) — complete with a private elevator, 21-foot ceilings, high-end finishings, a rooftop terrasse and spectacular views of Mount Royal.

The main space.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

The entire fourplex is being sold together at an asking price of $4,250,000. This includes the glass penthouse aka the main unit as well as three additional smaller units located within the older part of the building. That said, the other units were also renovated in 2018.

All the photos in this article showcase the penthouse.

Kitchen, dining room and spiral staircase.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

"Most people are looking at the main house for themselves and leaving the other three units for guests or their children," explained the listing agent Saguy Elbaz of Sotheby’s International Realty Québec. In the listing, he notes that this is ideal for a big family, hosting guests or generating rental income.

Large windows and a fireplace.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

The penthouse has three bedrooms while the other units — at 560 square feet, 380 square feet and 520 square feet — have a maximum of one bedroom, seeing as one is a studio.

The living space.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

There's a kitchen and dining area with a propane fireplace on the lower level and a living space with lots of natural light courtesy of the large windows upstairs. The two floors are separated by a sleek black spiral staircase.

A bedroom.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

There are also two bathrooms and a powder room as well as a garage and driveway parking spot included with the unit.

A bathroom.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

Beyond the glass cube, there are many more unique architectural touches that make this property a hidden gem!

A unique outdoor staircase.Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

So, is it what you imagined? Whoever moves in will surely have one classy — or shall we say glassy — abode.

Glass cube fourplex

The rooftop terrasse.

Courtesy of Saguy Elbaz, Sotheby’s International Realty Québec

Asking Price: $4,250,000

Address: 407-413, av. Édouard-Charles

View the full listing on Sotheby's International Realty