This post covers things I saw on 5 October, 2010.
Several times each day, I would walk between my hotel and Line 4's Xisi Station. Eventually I noticed that over the construction fence there were some golden-tiled roofs, which usually indicate something interesting.
So I walked around the corner and found the entrance to 广济寺 (Guangjisi), which is a Buddhist monastery and temple. Entrance is free.
As with the other temples I've visited in Beijing, it is somehow insulated from the hustle and noise of the busy street just outside its walls, creating a little island of peace and tranquility.
One difference between this and most of the other temples in Beijing is that this is an active religious facility, not just a historical relic. It is the home of 中国佛教协会 (the Buddhist Association of China).
It's not a very big temple compared to something like the 天坛 (The Temple of Heaven), but it's very nice in a humble way. One odd thing I saw there was a Buddhist nun wearing her robes wandering around in the parking lot, yelling loudly to no one in particular. I couldn't understand a lot of what she said, but she seemed to be complaining about things "they" were doing. If I saw a woman doing this in Seattle, I would assume a mental illness and hope she's getting treatment. On my way out, I saw a couple of civilians (not wearing robes at least) talking with her, apparently trying to calm her down.
It seems to be traditional that temples have cats, and my personal tradition is to take pictures of them.