Friendly advice - you're going to Beijing, not Peking.

Are you arriving by plane or on a cruise ship? If it's by ship the port is a fair distance from Beijing.

There's more than enough to see in Beijing for three days (or three weeks), I wouldn't bother with a side trip to Xi'an, although I suppose you could fly one way and take the night train the other.

Thanks Yes Beijing (used to airport codes).

Arriving by Plane Airport code PEK
Is the airport far from the main sites? What are the costs of public transportation from the airport? Night train there and flight back sounds great. Do you know which train station I would go from and to? Is the train station/airport far from where we would go see the Terracotta warriors?
Thanks again.
Laurel

For train info see seat61.com.

Suggest purchase of a guide book which will answer your other questions - my info is a bit out of date but you need a bus/taxi to get to the warriors.

With 72-hr transit without visa, you are supposed to stay within the municipality of Beijing if you're arriving at PEK. Nobody will or can stop you from leaving it by surface transportation, but if you fly out, the security may notice you are entering without visa.

Anyhow, there are so much to see and do in Beijing, you really should just stay there rather than trekking to Xian.

I agree with thursdaysd that a good guide book will prove well worth the investment.

And I agree with thursdaysd and rkkwan that there is so much to see and do in Beijing that trying to fit Xi'an in doesn't make much sense.

You might find some helpful information in my very long (but searchable) trip report - just click on my name to find it. The sections on Beijing are near the beginning and end.

Thank you all so much for the suggestions rkkwan was not considering the flying out as an issue? Great point.
looked at the train ideas via seat61.

Kja I will look at your trip report now.