US Doctrine of governmental 'taking'
The problem with your thesis is that under US law (legislation and precedent), if the City Council were to just zone the property as park or whatever, reducing the value of the property by $38.5 million, the present owner could take them to court for the difference in value. There are some circumstances under which it can be done, but in general any zoning or other action after the fact that reduces the value, or the owner's right to 'enjoy the benefits', without compensation for the lost value, is an illegal taking.
The most recent major case I can think of was in Oregon, where a business in Tualatin had a back parking lot that abutted the Tualatin River. The City decided to install a "River Walk" to allow folks to enjoy a walk along the river, and attempted to use Eminent Domain to take the land from the business. The business, which was about to lose several of its parking spaces, sued and won (IIRC after it went all the way to the Supreme Court). Had the City made the River Walk easement a condition of the original construction of the business, there would have been no case. This was about 10 years ago so I may not have all the facts right ...
What makes it interesting is that the right of the public to travel along the river is unimpeded - it's a navigable waterway. But there was no way to walk along it on that side at that point. I don't know what the final result was.