There are many ways that the new design for LOVE Park could have gone wrong. The square at the gateway to the Parkway is an engineering nightmare, perched above a parking garage and a train tunnel. The $15 million budget is barely adequate. And in the course of a series of public meetings, more than a thousand people offered the architects their two cents about how the space should look.

So it is remarkable that the designers, Hargreaves Associates and Kieran Timberlake, have found such an elegant solution to this impossible problem. The plan unveiled Thursday by the city's Department of Parks and Recreation is the Goldilocks of park designs. Not too formal. Not too relaxed. But just right.

The design balances the need for a certain amount of civic formality with our desire for a cozy, green refuge in Philadelphia's government center. There will be a green lawn where the public can throw down a picnic blanket. But the new design ensures that the iconic diagonal connection to the Parkway remains strong.

The plans also manage to preserve two important features from the existing park: the beloved "spaceship" building, and the jet of water that forms the picturesque backdrop to Robert Indiana's LOVE sculpture.

This harmony was missing in March, when the architects presented four interim schemes for the park, officially John F. Kennedy Plaza. Each showed a different combination of geometric forms. One was dominated by a semicircular lawn, the other by a square lawn.

Besides being overly fussy, none seemed to capture LOVE Park's place in the life of the city. The diagonal axis, which sets up a crucial relationship between City Hall's tower and the Art Museum, was barely visible, even though it is the most spectacular and photographed vista in the city.

The new design, which will be presented to the Art Commission on Wednesday, greatly simplifies the park's layout. Hargreaves, which is in charge of the landscape design, starts by dividing the park into two neat halves, separated by an east-west path connecting 15th and 16th Streets.

This time, it also embedded a strong diagonal path into the design. Instead of making it one straight line, it created a series of paved areas that hopscotch across the park's surface, from the LOVE sculpture at 15th and JFK Boulevard to 16th and Arch, where the Parkway begins. There will be no doubts that LOVE Park is part of the Parkway.

The centerpiece of the diagonal is an elongated oval with a fountain embedded in the paving. Like the fountain at Dilworth Park, the water can be turned on or off depending on what else is going on at the park. The fountain is a two-in-one design. At times, it will spout a towering jet of water. But it can also produce arcing streams. When all the arcs are in motion, the steams will braid together like a crystal basket.

In a nice detail, Hargreaves located the spout for the towering jet on axis with the round Welcome Center. It's also tucked a low bench on the western edge of the fountain so people can sit and watch the sprays.

One reason the design was such an immense challenge is that the park's surface slopes nearly eight feet from 15th Street down to the Parkway. The original design, by architect Vincent Kling and city planner Edmund Bacon, attempted to solve the problem through a series of stepped levels. But their design created high walls around the edges that made it difficult to see into the park.

Hargreaves replaces those granite terraces with a graceful slope. In doing so, it removes all the walls from the edges. The project's lead designer, Mary Margaret Jones, also expects to submerge the garage vents on the south side.

The changes will allow visitors to flow naturally into the park from all four corners, much as people do at Rittenhouse Square. Like all good landscape designs, this one sets up multiple pathways, allowing people to zigzag around its internal features. Some of the routes go through all of the trees. As part of the improvements, the stingy sidewalk along JFK Boulevard will be widened to a generous 12 feet.

The city has also fully committed to preserving the spaceship, now used as a visitor center. Designed by H2L2 in the late '50s and opened in 1964, it is a rare Philadelphia example of lighthearted midcentury design. But it has not been treated well.

Kieran Timberlake plans to reconstruct the building so it can be used as a cafe or wine bar. It will be fitted with new glass walls, a more elegant ramp, and handicapped-accessible restrooms. When it's finished in 2017, architect Richard Maimon envisions a terrace encircling the building. A perfect perch to admire a fine park design.