<P> The variation of plants can be explained by the change of climate in Rome through the centuries . Additionally, bird migration, flower blooming, and the growth of Rome that caused the Colosseum to become embedded within the modern city centre rather than on the outskirts of the ancient city, as well as deliberate transport of species, are also contributing causes . Another reason often given is their seeds being unwittingly transported either on the fur or in the feces of animals brought there from all corners of the empire . </P> <Ul> <Li> The Kongresshalle, or "Congress Hall", (1935, unfinished) at the Nazi Party Rally grounds, Nuremberg, Germany </Li> <Li> The Summer Olympic Games medal from 1928 to 2000, designed by Giuseppe Cassioli, features a depiction of the Colosseum . At the 2004 Summer Olympics in Athens the Colosseum was replaced by a depiction of the Panathinaiko Stadium </Li> <Li> The exterior of the Vancouver Public Library in British Columbia resembles the current state of the Colosseum . It was designed by Moshe Safdie . </Li> <Li> The Los Angeles Memorial Coliseum entrance was inspired by the Colosseum . </Li> <Li> The Palazzo della Civilta Italiana was very closely modelled on the Colosseum . It was built for Mussolini for the Universal Exhibition of 1942 but the exhibition never happened due to the outbreak of World War II . The architects were Giovanni Guerrini, Ernesto Bruno La Padula, and Mario Romano . </Li> <Li> McCaig's Tower, overlooking Oban, Scotland . </Li> </Ul> <Li> The Kongresshalle, or "Congress Hall", (1935, unfinished) at the Nazi Party Rally grounds, Nuremberg, Germany </Li> <Li> The Summer Olympic Games medal from 1928 to 2000, designed by Giuseppe Cassioli, features a depiction of the Colosseum . At the 2004 Summer Olympics in Athens the Colosseum was replaced by a depiction of the Panathinaiko Stadium </Li>

How many levels of seats did the colosseum have