As Boston officials finalize their pitch to Amazon for the company’s “second headquarters,’’ due later this month, they are firming up a list of possible sites for the e-commerce ­giant.

Along with the vast Suffolk Downs property in East Boston, the Walsh administration plans to propose perhaps three or four other sites around the city.

At City Hall, the nearly shuttered horse track remains a preferred location for the Amazon complex — with 161 acres and two MBTA stops, the site most closely aligns with what the company says it wants for a campus that could eventually be home to 50,000 jobs.

But the city is also considering sites closer to the core of the city, such as Widett Circle in South Boston, Beacon Yards in Allston, and maybe a cluster of properties in and around South Station.

Meanwhile, developers are pitching their own ideas, ranging from parking lots on the edges of the Seaport to downtown office towers. And there’s a regional proposal from Somerville Mayor Joseph A. Curtatone that would string Amazon buildings along the Orange Line from Assembly Row in Somerville to North Station in Boston.

Dozens of cities nationwide plan to bid for Amazon’s campus, but Boston is widely seen as a strong contender. The Walsh administration team working on the pitch is expected to settle on a handful of potential sites to include in the proposal, due Oct. 19.

The range of possibilities reflects the complex calculus bidders face in wooing Amazon. They must satisfy the company’s specific requirements, while also thinking “big and creatively,’’ as Amazon has urged. They also need to find a site that has room for expansion over two decades, yet will be ready for the company to start building on next year.

Then there’s the chance too much emphasis on real estate could distract from the heart of Boston’s pitch: the city’s vibrant innovation economy and well educated workforce. “We want to simplify this as much as possible, and tell our story,’’ said John Barros, head of economic development for Mayor Martin J. Walsh. “We’re not trying to create complexity here.’’

But in Boston, big real estate projects are never simple. Each site under consideration has complications — from tangled ownership to pressing infrastructure needs to land-use arrangements­ that would require cooperation from third parties like the Postal Service or Harvard University.

The initial appeal of Suffolk Downs was logistical simplicity: It has one owner (Boston-based HYM Investments), easy access to public transportation, and relatively clean site conditions. But it’s not centrally located, as Amazon’s main campus in downtown Seattle is.

“That’s not a site that speaks to a lot of what this city has to offer,’’ said Brendan Carroll, a veteran real estate analyst at Perry Brokerage who is consulting with several developers mulling sites for Amazon.

“I could show you a site like that four miles outside the central business district of almost any big city in the US,’’ he said.

A bolder approach, Carroll said, might be South Station, where the Houston developer Hines has most of the needed permits for a skyscraper that would rise 51 stories above the train tracks. That alone is not big enough for Amazon’s 8-million-square-foot requirement, but empty sites along Fort Point Channel, Kneeland Street, or the neighboring Postal Service distribution center could be incorporated in the plan, Carroll said. Hines declined to comment.

Other options being floated include a pair of Seaport sites — one owned by a subsidiary of Millennium Partners, the other by a firm owned by the Pappas family — or a strip of Dorchester Avenue in South Boston where new zoning allows 7 million square feet of office space.

Then there’s Widett Circle, the 83-acre swath of warehouses and rail yards south of downtown that was the centerpiece of Boston’s aborted Olympics bid. The Walsh administration has touted Widett as the chance to create a new neighborhood from scratch, but any project of that scale would need an anchor tenant such as Amazon. Property owners in the area say they would cooperate with the city on a pitch to Amazon.

“We’d love to be a part of it,’’ said Mike Joyce, a real estate broker representing a group of Widett Circle landowners. “It’s a gateway site.’’

Widett, like Suffolk Downs and the banks of Fort Point Channel near South Station, is among six areas outlined in the city’s new Imagine Boston 2030 plan as “expanded neighborhoods’’ that could accommodate large-scale development. Two other areas included in that report — Harvard-owned Beacon Yards in Allston and Sullivan Square in Charlestown — are also potentially in the Amazon mix.

Sullivan Square, a traffic-choked rotary lined by warehouses, could be part of a string of sites along the Orange Line, from Assembly Row to the mixed-use NorthPoint campus in Cambridge, to a planned office building at North Station.

That’s the option Curtatone is backing. He filed a preliminary proposal with the state Friday and said “Amazon on the Orange Line’’ should get a close look, even if it crosses city lines.

“We’re not miles apart here,’’ Curtatone said. “We see our region as incredible opportunity.’’

Tim Logan can be reached at tim.logan@globe.com. http://prdedit.bostonglobe.com/rf/image_1920w/Boston/WebLinked/2016-03-03/Business/Images/ryan_olympicsfrontageroad_biz[1].jpg