SAN DIEGO (CBS 8) - The future of the San Diego skyline is up in the air. Another developer has come forward with a proposal for a large attraction along the downtown waterfront.

The Skyspire would be about 300 feet tall and equipped with gondolas, which can carry up to 10 passengers each.

For under $20, visitors could spiral to the top of the tower where they could take in views of the city from an observation deck that would also boast a restaurant.

Four other developers are pitching their own visions - all in the form of Ferris wheels.

The FAA rejected a plan for a nearly 500 foot Ferris wheel because it would be dangerous for planes approaching Lindbergh Field.

However, the FAA did say a bayfront project that was no more than 277 feet high should not pose a problem.

The developers behind the Skyspire and the four Ferris wheel designs will each have a chance to present their proposals to San Diego's Port District Board next Tuesday.