Question: Where did the animals and scenery enter the colosseum?
About the article "Colosseum", section "Arena and hypogeum".

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The arena itself was 83 meters by 48 meters (272 ft by 157 ft / 280 by 163 Roman feet).
It comprised a wooden floor covered by sand (the Latin word for sand is "harena" or "arena"), covering an elaborate underground structure called the "hypogeum" (literally meaning "underground").
Little now remains of the original arena floor, but the "hypogeum" is still clearly visible.
It consisted of a two-level subterranean network of tunnels and cages beneath the arena where gladiators and animals were held before contests began.
Eighty vertical shafts provided instant access to the arena for caged animals and scenery pieces concealed underneath; larger hinged platforms, called "hegmata", provided access for elephants and the like.
It was restructured on numerous occasions; at least twelve different phases of construction can be seen.
The "hypogeum" was connected by underground tunnels to a number of points outside the Colosseum.
Animals and performers were brought through the tunnel from nearby stables, with the gladiators' barracks at the Ludus Magnus to the east also being connected by tunnels.
Separate tunnels were provided for the Emperor and the Vestal Virgins to permit them to enter and exit the Colosseum without needing to pass through the crowds.
Substantial quantities of machinery also existed in the "hypogeum".
Elevators and pulleys raised and lowered scenery and props, as well as lifting caged animals to the surface for release.
There is evidence for the existence of major hydraulic mechanisms and according to ancient accounts, it was possible to flood the arena rapidly, presumably via a connection to a nearby aqueduct.
A Roman-style Colosseum with a soccer field in the center.
This is where Joe found his Crest of Reliability and where Agumon dark digivolved into SkullGreymon. 
Attraction summary.
Guests queue outside the "Franklin Exploration Center", where it is presumed that they are waiting to board a helicopter which will taken them to "Base Station: Wild Arctic".
The queue outside the attraction includes numerous murals of the Arctic animals and scenery as well as various HD TV monitors that show various clips about the Arctic and its animals running on a loop.
Guests then enter the show building. 
The Vivarium was the location where the ancient Romans kept wild animals used in their entertainments.
It was near the Prenestina Gate of Rome.
During the first siege of Rome in the Gothic Wars, the Goths broke part of the wall of the Vivarium in an attempt to enter the city.
This attempt failed because the regular city wall manned by Byzantine soldiers was behind the Vivarium wall and Belisarius attacked the rear of the Goths near the Prenestina Gate.
According to the writer Charlotte Anne Eaton, a second, smaller vivarium was located near the Colosseum and was connected to it via a low vaulted passage.
This vivarium was located below the convent of St. John and St. Paul on the Cœlian Mount.
This vivarium was a practical necessity because of the considerable distance between the Vivarium by Porta Maggiore and the Colosseum. 
  Fights against wild animals in the arena of the Roman Colosseum were displayed in "Gladiator (2000)" and other films.