This was the reason for me (and I guess most other people) to come to Xi'an and one of the things I really wanted to see. I mean, I have seen pictures and replicas but nothing beats the real deal and in this case it is very impressive.
After an hour in the bus you arrive at the parking lot and have to buy your tickets there, then head for another 5 minutes or so through souvenir shops and food stalls until you reach the entrance to the museum, then another few minutes until you reach the actual museums and the pits containing the Terracotta Army as unearthed so far.
One tip here, you will see groups of volunteers at the entrances, these are students who want to practice their language skills so you can 'hire' them for free to be your guide and help you translate or interpret anything you might wish. While I would be weary of 'students practising their language' in China, here you can actually make use of them as they are nice and you will do them a favour.
Nonetheless, no matter what you decide, make sure you have some time on your own and wait till the groups (who come in waves) have passed to really enjoy and get a feel for what you are seeing and look at all the details.
Seeing the scale of the different pits, which are not even fully excavated yet, it's hard to believe how much time and work must have gone into this. Then you realise that every single soldier has a different face and hairstyle and they were all fully painted, it is indeed hugely impressive.
I will have to research this exactly but it is said the Qin Emperor took 35 years to conquer/unite China but the same time building his tomb. This by itself is mind boggling, also once you realise that these pits you are looking at are just a part of his tomb and you can see more and his mausoleum by taking a free shuttle bus to another site around 1.5km away.
While you won't see much there other than a very large park and a mound/hill, if you imagine what lies beneath all of this it will be very impressive (at least it was for me).
If you ever get the chance, you have to come and see this, it's one of the things you have to see for yourself, like Angkor Wat and the Pyramids.
After taking the bus back and picking my stuff up at the hotel, I am now sitting in the very comfortable bullet sleeper train to Shanghai. So far I have a compartment for myself but this could change later on.
Tomorrow morning I will arrive in Shanghai and head after having some breakfast to Hangzhou for a few days before heading back to Shanghai and on to Suzhou.