The Denver Zoo considers itself a city within a city, with animal citizens whose upkeep is subject to the same rising costs many people in the metro area are facing. That’s why the zoo is seeking an admission increase — the first since 2014. The zoo wants to raise the price of tickets to $20 from $17 for those 12 and older; to $14 from $12 for children; to $17 from $14 for folks 65 and older.