What will happen to the Citgo sign?

The string of buildings Boston University is selling in Kenmore Square is unremarkable except for one thing: The most famous sign in Boston sits on top of one of them.

And that could prove a challenge for whoever winds up buying them.

As several prominent development companies angle to buy the nine-building package, they are weighing a delicate question: how to redevelop them — as any new owner would be likely to do — without blocking or moving the sign so it is no longer so visible from so many places around the city.

“I was not going to be ‘that developer’ who would take down the Citgo sign,” said Ted Tye, managing partner at National Development, which considered bidding for the properties but chose not to. “It’s such a symbol of Boston.”

In January, BU, which owns the six-story 660 Beacon St. and leases space on the roof to Citgo Petroleum Corp., put the building and others around it up for sale. It has received a number of bids, said a person with knowledge of the matter, and there are at least three prominent local developers still in the running as potential buyers.

BU declined to comment, as did several of the prospective bidders.

But whoever buys the buildings will face an immediate challenge: how to make the most of the investment — likely to be in the millions of dollars — without disrupting the sign or blocking views of it across the city.

Or they could face a fate even worse: being known as the person who took it down.

Moving the sign and replacing 660 Beacon with a taller building wouldn’t be difficult, said Arthur Krim, a faculty member at Boston Architectural College and the sign’s unofficial historian. But move it much, and the views would be altered forever.

“Sightlines would be skewed,” Krim said. “Anything above 15 stories and it’d be hard to see up there at all.”

The issue, added Tye, is that a new owner probably could not raise the sign more than 30 feet without drastically altering the sightlines. Nor could neighboring properties be replaced with taller buildings without blocking the Citgo sign. And any major work would probably involve dismantling the sign and putting it back up later.

“Is all that effort worth it for an extra 30 feet?” Tye said. “In a city like Boston you say, ‘What’s iconic on the skyline’ and this is part of it.”

BU has argued that the famous sign boosts the value of the property, but acknowledged the sign’s future is ultimately up to the new owner. Because the Citgo sign is not protected by landmark status, preservationists are pushing BU to include restrictions in the terms of the sale.

A sign from what is today known as Citgo Petroleum has been part of Boston’s skyline since 1940. In 1948, it read “Cities Service.”Globe File/1948

“BU could be much more clear about what can happen here,” said Greg Galer, executive director of the Boston Preservation Alliance. “This is a potentially dire situation. There is no commitment on the table that the sign stay in place.”

Citgo is lobbying to keep the sign in place, and earlier this spring launched a website and an advertising and social media campaign devoted to “Boston’s Sign.”

“More than a sign, it’s an icon,” reads the website, above dozens of Instagram pictures of the sign with Bostonians in front of it.

Neighbors for whom the sign has become part of daily life are keeping an close eye on the sale. Krim said he even discussed the sign with Red Sox officials at Fenway Park recently. A spokeswoman for the team declined to comment.

The Boston Athletic Association has been watching, too.

“It’s hard to imagine the landscape of Kenmore Square or what the city would look like there without the Citgo Sign,” BAA spokesman Jack Fleming said. “But I’d stop short of saying it’s something we’d get involved in.”

Ultimately, the issue could wind up at City Hall. Any significant construction would need Boston Redevelopment Authority approval, and while the sign has no formal protection, that process would give its many fans a venue to argue for saving it.

The BRA is monitoring the sale, spokesman Nick Martin said, and has formed an “internal cross-departmental working group” to evaluate potential plans for the Kenmore Square properties.

“We will remain in close contact with BU and look forward to facilitating a broader public dialogue when the time is appropriate,” Martin said.

Still, big-money real estate deals have a way of gathering momentum, Krim said. Whoever pays for BU’s buildings will want to put their own stamp on them, especially in Kenmore Square, where the pace of redevelopment is picking up.

And even with the best of intentions, Krim worried, that kind of momentum could spell the end for the light-up billboard, which has long been part of the city’s face.

“The sign may have ingrained itself in the civic iconography of this town,” Krim said. “But in fact, it’s only goodwill that has kept the sign lit.”

Fenway Park and Kenmore Square.David L Ryan/Globe Staff