I agree with this. I often go through Hart Plaza, but for the sole reason of getting to the Riverfront. Hart Plaza can either be a space for events, or it's a giant, decaying concrete jungle, and never anything in between. I would love to see it drastically redesigned. I just returned from a trip to Boston and their public spaces were much better.
As to the question of bridge or tunnel, I would say a decorative bridge is the way to go. It has to look good, or it may damage the perception of downtown.
I fear a tunnel would have rumors of crime, true or not.
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