Public investment in the soon-to-open Colorado Convention Center expansion and the accompanying Hyatt hotel appears to be paying dividends, with more than 800 new hotel rooms planned for downtown Denver.

Planned new hotels and expansions of existing properties, combined with the 1,100-room Hyatt Denver Convention Center Hotel now under construction, will increase the room supply downtown by 35 percent. That would make a total of about 7,200 rooms.

With the doubling of the size of the Colorado Convention Center, the city will draw groups that couldn't hold annual confabs there before because they were too big for the original arena. And the building, with two main entrances, will be able to handle the comings and goings of more than one sizable convention at a time, cutting the lulls between groups.

But it will be years before the city sees the full impact of a project that cost more than $306 million and has been a decade in the making.

The city will hold an official ribbon-cutting ceremony for the center Dec. 6. "We have a saying in our industry: You can build convention facilities faster than you can sell 'em," said Richard Scharf, president and CEO of the Denver Metro Convention & Visitors Bureau.

The bureau just recently snared a two-week-long series of meetings revolving around the National Education Association's annual event. It's the city's biggest convention reservation in terms of the sheer number of hotel room nights to be booked: 56,000.

To date, groups have booked conventions as far out as 2017. In all, the visitor's bureau estimates, they will bring $1.3 billion in spending to the metro area while they are here.