Hello how may I help you? What's the tallest building located in Denver, Colorado? The tallest building in Denver is the Republis Plaza. How tall is it? The Republis Plaza is 357 feet tall. Do you know what's the tallest building in New York City? The tallest building in New York City is Trump Tower. How tall is it? Trump Tower is 9000 feet tall. Which city has the highest population? Los Angeles is the most populated city with 5.3 million people living in it.