A lot of Detroit developments have hit roadblocks lately, largely due to construction costs increasing.

But a new study makes note of what actually is being built: $3.4 billion worth in and around downtown Detroit, according to the Royal Oak office of Chicago-based brokerage house JLL.

More than half of that tallied is by billionaire Quicken Loans Inc. and Rock Ventures LLC founder and Chairman Dan Gilbert across the development on the site of the former J.L. Hudson's department store downtown ($1 billion, give or take, although we still don't know exactly how tall it's going to be); the Wayne County Consolidated Jail complex project at I-75 and East Warren Avenue ($533 million); the redevelopment of the Book Tower and Book Building on Washington Boulevard ($313 million); and the City Modern project across 8.4 acres of Brush Park land ($100 million-plus, but we've never gotten a precise amount).

Others included in the JLL overview are Ford Motor Co.'s $350 million redevelopment of Michigan Central Station in Corktown and the Ilitch family's new Little Caesars Global Resource Center ($150 million). Billionaires and billionaire families, all.

The majority of those projects have been many years in the making.

Harrison West, senior research analyst at JLL, went back to 2012 and tallied construction projects completed or announced valued at $1 million or more: 167 in total representing at least $10.4 billion (including the QLine).

Of that investment figure, 35 percent has been completed, 33 percent is under construction and 32 percent hasn't yet started.

You can view the project maps here.