Downtown Boston real estate is expensive. And yet a whole bunch of that space is wasted on parking lots for suburban commuters. But while Greater Boston has expanded north, west, and south over time, what if it could expand eastward as well? An article this week at Fast Company’s Co.Exist site reported on an interesting solution to urban congestion: building on water. As the article explains:

A Dutch architectural firm believes it has some of the answers to dynamically growing cities with floating islands of infrastructure. A city could add a floating car park for a couple of years, and then move it to another location, says Dutch Docklands’ Jasper Mulder. “It’s more dynamic and all you need is water,” he says. “Movable floating infrastructure can make it possible to do so much.” When the building is no longer needed–say, when a big event is finished–it can be detached from the land and sent elsewhere.

Made of foam and concrete, these platforms would be anchored to the sea floor and would have little to no ecological impact, according to the firm.

As a big proponent of the economic and environmental benefits of urban density, I can’t help but be intrigued. As long as the center of Boston is downtown, yet another expansion eastward seems sort of inefficient. Adding capacity to the city directly adjacent to its most valuable real estate seems preferable.

So what else could these platforms be used for other than parking? Floating beaches or cruise ship docks, even parks. Maybe Streetwise Media could set up a floating office, parked next to Boston but ready to float down the East Coast on a moment’s notice.