What next, Mr. Mayor?

Our Mayor For Life wants you to know that he is not out of gas. Not at all.

In February, speaking before a packed house at the annual Boston Municipal Research Bureau luncheon, our MFL unveiled his cry for attention, I mean, Big Idea: a 1,000-foot downtown tower, a symbol of "the full scope of this city's greatness." Yesterday morning, before another packed breakfast crowd at the Greater Boston Chamber of Commerce, MFL offered another Big Idea: selling City Hall and building a new one on the waterfront. He wisely omitted the words "on budget and on time."

No fourth-termitis for this administration. MFL has a packed calendar of high-profile events coming up, and needs something surprising to say. Otherwise someone might be inclined to ask him why city residents are paying ever-higher property taxes and getting less for their money. Or what he's doing about the slaughter of black people by black people in Roxbury and Dorchester.

Next month, MFL gives his 14th State of the City address. According to well-placed City Hall sources, MFL will use the occasion to roll out yet another Big Idea: an elaborate canal system in the shape of seagull in flight that will at long last link the Charles, the Neponset, and the Muddy rivers into a seamless 16th-century transportation network and bring a little Italy to all of Boston. The preliminary plan, which MFL is said to have sketched out on a napkin at Mike's City Diner, calls for duck-boat-like gondolas, "Tommy's Tours," to navigate the canals. There will also be limited use of Jet Skis, party barges, and water slides where appropriate. MFL pal Connie Kastelnik is said to have the inside track on the Jet Ski concession.

MFL's brain trust is still vetting Big Ideas for the mayor's return engagement before the Municipal Research Bureau in March. Among Big Ideas under active discussion, say City Hall sources: a soaring Tower of Mumble on the Rose Fitzgerald Kennedy Greenway or a Sphinx -like monument in the likeness of the MFL in the neighborhoods, most likely his beloved Readville. Residents are urged to call in their Big Ideas to City Hall at 617-635-4000. The Big Deadline is Feb. 1.

City Hall has problems, but it could be fixed. We had a reasonable plan on the table a decade ago. But it is ultimately the builders, not the fixers, who are remembered. And the most important part of really Big Ideas like these: Anyone who starts a job this big can't possibly leave before it's done. It wouldn't be right. How long will it take to complete a new City Hall or the canals? Another term? Or two? Or three?

Once upon a time, MFL was derided as Mayor Pothole, a guy who lacked vision but whose heart was firmly in the neighborhoods. But at some point, even MFL knows when he is closer to the end than the beginning, and it comes time to think legacy. If you can't do anything about the neighborhood killing fields or rising property taxes, better to focus on what you can -- building a monument. Or two. Or three.

Steve Bailey is a Globe columnist. He can be reached at bailey@globe.com or at 617-929-2902.