Editor's note: Here's another of our most important stories of the past year.

The Children's Museum and Seattle Children's Theatre are deeply in debt to Seattle Center, owing rent payments in the six-figure range and putting them among the Center's largest debtors.

The Children's Museum, a 31-year-old attraction in the basement of the Center House, owes $513,340, more than any other tenant or one-time renter of facilities at the expansive, city-run Seattle Center. The Intiman Theatre, whose problems have been reported recently, holds the second-highest debt, $308,942. The Children's Theatre, located in a standalone building near the southwest corner of the site, owes the third most, $167,670.

In total, the Center is owed $1.1 million in back rent, and $836,000 of that is over four months past due. The figures underscore the pressure city administrators are under to find new tenants that are at least self-supporting and, ideally, that could generate revenue for the city. (Note: This paragraph originally said the Center is owed $1.5 million in rent. It has been updated to reflect that $428,012 of that rent is not past due, but part of the current billing cycle.)

That pressure has come up this year as Seattle Center looks for a tenant to replace the financially strapped South Fun Forest carnival. Glass artist Dale Chihuly and the owners of the Space Needle proposed a paid-admission glass museum for the area, at the base of the Needle, but public criticism of the idea early this year led to a review, which is still ongoing.

The overdue rent records, released by the Center late Monday in response to a public-records request, show debts as of Oct. 31. And some organizations' tabs are growing by monthly rent amounts of more than $10,000. Center spokeswoman Deborah Daoust said the agency is working with its tenants to negotiate payment schedules. The full list of debts can be seen here.

The Children's Theatre reached an agreement several months ago, and the museum and Intiman are negotiating payment schedules now, Daoust said. Even so, it could be years before the Center collects what it's owed — if it ever does.

"We don't normally do penalties," Daoust said, adding that in the past the Center has levied late-payment fines that have been excused once a case goes to collections at the central city-government level.

Donna Marie Bertrand, executive director of The Children's Museum, said that like many nonprofits, her group has been hit by decreasing contributions from individuals, corporations, and governments, along with falling ticket revenue, due to the recession. In addition, the museum provides reduced admission to schools and groups that serve disadvantaged kids, a need that has increased.

"It's a real double-whammy," she said.

Bertrand said the museum was already in arrears when she took the head job in July 2009. She immediately began tackling the debt, and the group has been making weekly payments ever since. "We do want to honor our debts and we are making progress on that."

Still, the total amount owed has been increasing because the agency can't keep up with its $16,419 monthly rent. And the total owed by now — over a half-million dollars — represents nearly a third of the group's $1.7 million budget for this year.

Though it could be five years before the museum is caught up, Bertrand said, she is not concerned about its survival. She has seen "ebbs and flows" in business and education during previous jobs, she said. "And the Seattle Center is a huge partner in making sure that we are successful."

The two-page list of accounts receivable released by the Center shows 12 groups owe payments that are more than 120 days late — bills ranging from $7.12 to the museum's half-million-dollar amount. Debtors include the well-known nonprofit arts groups as well as for-profit concessionaires such as the Center House Bistro & Bar, owing $46,865, and the Bubbles Inc. candy store, owing $28,503. Giant Magnet, which puts on the annual International Children's Festival, owes $42,900.

Intiman Theatre, whose Center debt was detailed in this recent article in The Seattle Times, has struggled for years to get out of debt. Its tax filing for the 2008-09 season showed the theater losing $518,000 for that year.

Daoust said the Center had worked out one payment plan with Intiman, but she said, "They weren't able to keep up with those last year." So the city escalated the negotiations and is now working with the finance committee of the group's board.

All of these problems help explain why the Center was quick to warm to the idea of a Chihuly glass museum in place of the kiddie rides have entertained families for decades. The museum's proposal offered $350,000 a year in rent, jumping to $500,000 after five years. Center staff came close to striking a private deal with the museum proponents, but when it became public, there was enough controversy over the idea and the process that the Center ultimately solicited bids.

The Center's Request for Proposals listed six criteria on which the ideas were to be judged, and three of those mentioned money — capital investments and rent income, for example.

An appointed panel reviewed nine proposals and recommended the Chihuly plan. Mayor Mike McGinn is now considering the issue and hopes to make a recommendation to the City Council by the end of December, spokesman Aaron Pickus said. Ultimately, the Council will make the final call. Popular alternatives have included a new studio for alternative-rock station KEXP and a Native American cultural center — or some combination of those with a glass museum.

(Editor's note: Crosscut Publisher David Brewster was behind a proposal to have open space at the Fun Forest area.)