Hello, how may I help you? what is the tallest building in Denver? That would be the Republis Plaza. How tall is it? 10000 feet tall. Is it taller then the Eiffel Tower? Yes, it is twice the size of the Eiffel Tower. What is the second biggest building in denver? That would be the Dublis Tower. how tall is it? 9000 feet tall. Great. Thank you.