Amazon has triggered a $5 billion bidding war — here are 10 of the most ambitious site proposals for its new headquarters

At least 50 cities in the United States and Canada are expected to submit proposals for sites they believe would be the best fit for the e-commerce giant.

For some cities, the offer sounds too good to pass up. Many are offering generous tax incentives and opportunities to develop huge swaths of land to the company.

Here are some of the most ambitious sites that cities are proposing for HQ2:

Chula Vista, California — an 8 million-square-foot site near the US-Mexico border that would include "the world's first binational university"

McKinney, Texas — a 2,500-acre development for 30,000 people

The North Texas area is proposing several sites for Amazon's HQ, including one that would include a 2,500-acre planned district in McKinney, Texas, according to Dallas News.

Located around 35 miles outside Dallas' downtown, McKinney wants to entice Amazon to

The project is expected to house 30,000 people, and include two lakes, 300 acres of green space, farmers markets, a 200-acre office park, and commercial space.

Dallas, Texas — a development surrounding a proposed station for a $15 billion bullet train

Developers from the firms Matthews Southwest and Texas Central Partners arepitching a transit-oriented developmentfor Amazon's HQ2 campus, according to the Dallas Business Journal. It would surround a proposed station for a bullet train, which Dallas magazine reports is expected to cost$15 billion. If approved by the city, the 240-mile line will transport passengers from Houston to Dallas in 90 minutes.

Houston Mayor Sylvester Turnerhas formally expressed supportfor the train plan, which is likely to happen with or without Amazon. Developers hope to start construction on the development by late 2018.

Chicago, Illinois — a redeveloped site of a former hospital

Chicago developers recently unveiled renderings of its bid, dubbed the "Burnham Lakefront," Curbed reports.

The plan, which will go ahead regardless of Amazon's choice, features a redevelopment of the former Michael Reese Hospital site near the city's South Side. The lakefront property has been vacant since the hospital was demolished in 2009.

Amazon's mixed-use campus could be as large as 14 million square feet, depending on market demand and tenant needs, the developers wrote in their bid. The site would have office space in high-rise towers, housing that would span 144 acres, public plazas, landscaped bridges, and .

Philadelphia, Pennsylvania — three sites that would collectively span 28 million square feet

Amazonsaid it was looking forexisting buildings of at least 500,000 square feet and total site space of up to 8 million square feet.

Philadelphia would go above and beyond that requirement. Its officials areproposing three sites to Amazonthat would collectively span an estimated 28 million square feet in the city, according to The Philadelphia Inquirer.

The unfinished developments — Schuylkill Yards, uCity Square, and Navy Yard — already include millions of square feet of offices, retail, transit lines, and residential spaces.

Baltimore, Maryland — a waterfront site planned by Under Armour's private development firm

Maryland governor Larry Hogan has promised Amazon space in Port Covington, a planned district in Baltimore, according to The Baltimore Sun.

The mixed-use, $5.5 billion site, which will be anchored and developed by Under Armour, will feature

Hogan would not disclose any of the proposal's details, but sources have told The Sun the state's incentive package for Amazon would measure in the billions of dollars. Plans for Port Covington have garnered local controversy, since Baltimore City will pay $535 million for its development.

Huntington and Long Beach, California — three sites in a campus that would be named "Amazon Coast"

In a collective bid, Huntington and Long Beach, California have envisioned what they call " target="_blank"Amazon Coast."

It would be made up of three sites — one in Huntington Beach (called "Amazon Sand"), another along the Long Beach waterfront (called "Amazon Sea"), and a third next to Long Beach Airport (called "Amazon Air"). In total, the three sites would allow for 11.4 million square feet of space for Amazon.

Phoenix, Arizona — a proposal to move inside a renovated shopping mall

Phoenix officials are pitching a redevelopment of the city's Park Central Mall to Amazon, according to multiple sources who spoke with the Phoenix Business Journal.

Park Central was the city's first mall when it opened in the 1950s. The mall's clothing stores shut down several years ago, and today there is just a Starbucks, a few restaurants, offices, and a data center.

Sacramento, California — 12 potential sites, including a neighborhood with 4,000 housing units

The Sacramento area's HQ2 bid includes a dozen potential neighborhoods for Amazon, according to The Sacramento Bee.

The regional proposal, which was submitted by

New York City — a bid that includes possible sites in three boroughs

New York City's HQ2 bid is offering sites in Midtown West, the Financial District, the Brooklyn Tech Triangle, and Long Island City, according to the New York City Economic Development Corporation.

In Midtown West, the city says there is over 26 million square feet of space — in a range of building types from office towers to "historic gems" — for Amazon. There is over 13 million square feet of space available in Long Island City, and 8.5 million square feet of potential space in the Financial District in Lower Manhattan.

Finally, there is over 15 million square feet available for HQ2 in the Brooklyn Tech Triangle, which includes DUMBO, the Brooklyn Navy Yards, and Downtown Brooklyn. The bid doesn't include specific design plans for any of the proposed sites.