A giant national park that is likely filled with asbestos, lead, and god knows what other toxic substances they used to use in buildings back in the day. Tearing all these buildings down carries serious environmental risk.

$50 million? Dunno...

There's been a lot of investment in 'downtown' over the last decade - new ballparks, office buildings, etc., so those alone would probably need more than the $50 million I mentioned, but if you exclude those...

Unfortunately, a lot of prime, undeveloped real estate is owned by aggressive squatters with enough money to make any such venture a living hell.

I feel like that would be counterproductive- circling the (not bad) downtown with miles of undevelop-able land.