Hello how may I help you? Can you tell me what the tallest building in Denver, CO is? Its republic plaza What is the second tallest? 1801 California Street do you want to know their heights? Awesome! Yes, that would be great! Republic is 714 feet and 1801 California STreet is 709 That is crazy! I know. anything else? Nope, that is all. Thanks! have a nice day