1. Great Heights

In 2004, husband-and-wife developers Randy and Steve Fifield spied a prime, eight-acre parcel in downtown Chicago, the largest undeveloped lot within walking distance of the West Loop’s many office buildings. The five-tower residential complex they built on the site has helped trigger the change from daytime work corridor to hip 24-hour residential hub. The last tower, K2, is named for a mountain second only in height to Mount Everest. The highly amenitized rental apartments opened in March.

2. Urbane Urban

To appeal to its young tenants, ages 25 to 34, the Fifields incorporated sophisticated design, lots of light and air, and top materials, products, and technology. Collaborations with architect Brian Kidd of Pappageorge/Haymes Partners in Chicago and interior architect Sally Cathcart of Adrian Smith + Gordon Gill Architecture, also local, led to selections such as high-end faucets, marble flooring, Wi-Fi, and in-unit, in-wall speakers synced to Bluetooth amplifiers. The building also was designed for LEED Silver certification.

3. Green Inside and Out

The team located K2’s entrance on the third level, due to a slope, and placed parking beneath, with electric car-charging stations. A grove of birch trees welcomes people at the front door and promotes a calming effect. Cathcart carried through a mix of natural textures and tree motifs inside with wood furnishings and a huge digital print of birch trees, and added a modern, warehouse edginess in metal materials and cool, blue accents. The Fifields even lent some of their art collection, including 10 Salvador Dalis.

4. Social Networking 2.0

Having the latest amenities in public spaces was another necessity to attract young professionals. “We had to sell a lifestyle, and it’s a game of increments to lure someone to your building instead of to another,” says Kidd. Perks were organized on one level for ease and include two lounges; a party room with a kitchen; a theater with café-style seating and tables; a yoga studio; a basketball court; a coffee bar; and doggie day care. A concierge orchestrates activities, including parties, classes, and charitable events.

5. Solo Suites

Because so many young professionals prefer living alone, the developers designed 86 percent of the 496 units as studios and one-bedrooms. To compensate for the small square footage—765 square feet, on average—units were made to resemble boutique-hotel rooms, with luxury finishes and cabinetry; key-card entry; deluxe bathrooms and walk-in closets; stainless steel appliances; granite countertops; many floor-to-ceiling windows; and more. Monthly rents range from $1,350 to $6,500. —Barbara Ballinger