Can you walk across Central Park during the New York City Marathon?

Technically yes, you can, but you will probably have to take some major detours, since the race ends with the runners coming down the Park Drive, to the finish line at Tavern on the Green (on the Park Drive at approximately 66th Street).

However, even if you have to take some major detours, walking is still your best option, since the traffic through the park will be so jammed up.