It's sad, really. The Detroit Riverside Hotel (be honest, have you ever heard that name before?) sort of gets lost in the shuffle whenever people do a head-count of "Detroit buildings that aren't used." Maybe its status as a vacant building isn't old enough to qualify, kind of like Brennan Bosch and his batting average.
Anyway, the Riverside Hotel is more commonly remembered as the Pontchartrain Hotel, a 1960s-era hotel designed to offer a river view to anybody staying in any of the hotel's 367 rooms. That explains the jagged design; pretty crafty.
The Pontchartrain was a popular place through the 1970s, even hosted George H.W. Bush during the Republican Convention in 1980, but it's been all downhill from there. Investor Charles Keating got involved during the 1980s, and we know how most of his work turned out.
Most recently a group tried to breathe new life into the Pontchartrain by renovating it in 2007 and renaming it the Detroit Riverside Hotel. They apparently weren't discouraged that the hotel isn't really that close to the river. Unfortunately, the renovation failed, the hotel went into foreclosure in August of 2009 and it's been standing there quietly ever since, just waiting for the day when people will shut up about the old Michigan Train Depot and pay a little more attention to newer, shinier vacant buildings.