What's not free: the city will pay for part of the cost of a tunnel for Metra trains that pass to the east of the proposed tower and for a public riverfront park to be built on top of the underground structure. To come up with the $29.5 million for the work, the city will tap reserves from a downtown special property-tax district originally designed to promote development in blighted areas. The developer will pay an additional $30 million for the tunnel and park, according to mayoral spokesman Tom Alexander.