The confluence of the Chicago River and the North Branch is getting its third major skyscraper project in recent years.

The property formerly known as 400 West Randolph Street is now going by the name of 150 North Riverside, and its developers, John O’Donnell and U.S. Equities, are putting up one of the few remarkable office building designs the city has seen in a long time.

Like River Point, its neighbor currently under construction to the north, 150 North Riverside has to contend with the Amtrak tracks that run down the west bank of the river. Like River Point, 150 plans to deck over the tracks with a public park. Unlike River Point, 150 doesn’t have space to push the tower back from the water’s edge and avoid the trains. So the plan by Goettsch Partners is to every-so-gently insert the building amid the tracks with as small a footprint as possible, and then spread out once it reaches a certain height.

It’s an unusual design, but not unprecedented. The Rainier Tower (1301 5th Avenue) in Seattle is a great example of accomplishing something similar. Also, Qube (1383 West Georgia Street), in Vancouver, British Columbia also makes space below its main mass. Though instead of sprouting like a flower the way Rainier Tower does, and 150 North Riverside plans to do, Qube is actually a building hanging from a center pole via steel straps. (You may recognize Qube as the headquarters of the fictional Phoenix Foundation in the MacGyver television series.)

150 Riverside’s neighbor to the south, the Boeing Headquarters, uses a combination of these techniques — a reduced footprint to avoid the tracks, and a portion of the building suspended over the tracks. In Boeing’s case, by a metal framework.

The advent of 150 North Riverside, should it actually be built, means the end of the epic views for a lot of people at the Randolph Place Lofts (111 North Canal Street). Though it appears the tower has been placed on the northeast corner of the plot in order to reduce disruption, in a city of this size and an area with this density, you can’t build a hot dog cart without getting in someone’s way.

The parcel is a complicated one to build on. It consists of four pieces of land. The land running north-to-south along the river if officially 400 West Randolph. It’s on this strip that the office building would be located. The land running north-to-south along the Randolph Place Lofts is a different plot of land, 418 West Randolph. And then a third chunk of land at the corner of Lake Street and the Randolph Place Lofts is 417 West Lake Street. Running down the middle of all of this are the Amtrak tracks, which are on their own land.

You may remember that Mr. O’Donnell bought the land along the Chicago River late last year. The previous owner wanted to put up a 50-story tower with offices, residences, and a hotel, but was unable to make the plan fly.

To make this latest plan work, O’Donnell will need to buy 418 West Randolph and 417 West Randolph from the City of Chicago, as well as negotiate for air rights over the Amtrak railroad tracks.

Earlier this year, Crain’s Chicago Business reported that he planned to put up a 1.2 million square foot tower on the 400 West Randolph plot, but that idea was torpedoed by 42nd Ward Alderman Brendan Reilly. The developer wanted $20 million from the city for his development, then instead decided to ask for the land at 417 and 418 for free. Reilly is perhaps best-known for his philosophy that pretty much any large development going up in his territory must contribute something positive to the city’s urban fabric. A $20 million hand-out, and free land from the city don’t qualify. But the park we see in the new drawings may be that public give-back that Mr. Reilly is looking for.

We’ll know more about the project by the end of the month. As always, keep watching our Twitter, Facebook, and RSS feeds for more information as it comes out. You can also sign up for our e-mail newsletter to stay up to date. There’s a signup box at the top right of this page.