So we’ve got a city-approved plan to raze and replace KeyArena.

When it opens (tentatively in 2020), it’ll be the third different building on its Seattle Center site, under its landmark concrete roof beams, in nearly six decades.

Here’s a brief history of these structures:

Coliseum I, aka “Coliseum Century 21” and “the Washington State Coliseum.”

Built for the 1962 World’s Fair (aka the Century 21 Exposition), its inside attractions included a scale model of a future Seattle (where the Coliseum was one of the last “old” Seattle buildings still standing in a futuristic model city tableau) and the still-remembered Bubbleator.

Part of the fair’s mission had been to incorporate existing buildings (the Armory, Memorial Stadium, the Civic Auditorium/Opera House/McCaw Hall), and to add permanent new buildings (the Space Needle, Pacific Science Center, the Playhouse). Among these was the Coliseum, planned for post-Fair conversion into a big arena.

At the time, the only team scheduled to move in was the first Western Hockey League’s Seattle Totems.

One of the first big events: the Beatles. Since then, it hosted both the Sonics (the 41-season NBA team) and the Sonics (the legendary Tacoma garage rockers); as well as the Who, the Stones, Hendrix, Led Zep, Diana Ross, and Nirvana’s last Seattle shows.

Coliseum II, aka KeyArena.

The Sonics’ then-ownership and the NBA demanded more luxury suites and other new amenities. The original Coliseum was razed, except for the trademark “roofline,”

The new place had 17,000 seats (3,000 more than the old place), in line with most new basketball arenas of the time. But it was deliberately made hockey-unfriendly. A full-size rink was installed, but it could only be used if one end of seating was folded away.

KeyArena was used for NBA basketball for only 13 seasons, before the Sonics were grabbed and moved away. Our junior-level hockey team, the Thunderbirds, decamped to Kent soon after. Since then it’s remained home to the WNBA’s Storm and become home to the Seattle U Redhawks.

But its biggest year-round use, again has been in bigtime concerts.

Coliseum III, name to be determined (the “naming rights” will be sold to a new sponsor).

It’d take several times this space to even summarize the past nine years’ worth of drama: the many parties (most notably Chris Hansen’s Sodo arena group) that tried and failed to build an all-new arena; Hansen’s failure to buy an existing NBA team; the fatal City Council vote not to let Hansen take over an under-used side street; the emergence of two different KeyArena replacement schemes; the long negotiations to get the all-privately-funded OVG plan established and approved; the surprising role played in the negotiations by Councilmember Debora Juarez (one of the five women on the Council who’d rejected Hansen’s street-vacation request).

Final documents have to be signed, and a traffic master plan approved, before construction can start. The plan is to have the 1995 arena razed starting early next year, and to have the new place done by October 2020.

During construction, the Storm and the Redhawks will need other quarters. The Seattle Center Skatepark will be permanently replaced by a new facility somewhere.

The Northwest Court buildings, now housing KEXP, the Vera Project, and the SIFF FIlm Center, will stay. They had been threatened by one of the early arena-replacement schemes.

The new place will have twice the total square footage of the current one. It’ll have only about 350 more total seats; but it’ll have more luxury suites, and far better concert facilities and acoustics.

And it’ll fit a full size hockey rink, without sacrificing seats or sight lines.

Already, rumors are spreading that the National Hockey League will drop a new franchise our way, to begin play as soon as the new building’s ready.

In a classic “cart > horse” situation, folks are already talking about what to name the NHL team we’re supposedly just a few years from getting.

People have Tweeted, texted, and written in to media outlets with suggestions: Thunderbirds, Totems, Metropolitans (our team that won the 1917 Stanley Cup), and Steelheads (the name of our one-season Negro Leagues baseball team).

One wag at ESPN even suggested “Thunder,” just to spite the gang that stole our NBA team.

CLARK HUMPHREY is a columnist on Seattle culture. “LOSER: The Real Seattle Music Story” is now available from miscmedia.com and other online sources.