Get off at the subway at the Sanshanjie stop on Line 1 and meander east to find the Confucian Temple area. It's pretty obvious, as there are three arch gates leading off the main streets into the pedestrian-only (you can get a rickshaw) streets of the Temple area.
It's largely a tourist attraction catering to Chinese tourists, though as laowei ("old foreigner" in Mandarin) you'll attract immediate attention. Keep a smile on your face and make eye contact, and you'll probably get a chance to talk with some (usually young) person who'll say, "Hello!" and sometimes trot over to talk, part to practice English and part because the Chinese are generally friendly, curious, and cheerful people. You'll also, in contrast to almost everywhere else I've been, almost always get a smile and nod in return if you persist. Even the little old Chinese ladies with initially suspicious looks on their faces thawed when I applied the eye-contact-with-big-grin ploy, even though (or perhaps because?) I'm a 2 meter-tall white devil wearing a tie-dye and cowboy-style hat.
Anyway, the temple is lovely, if rather small. Many of the items inside are obviously reproductions of the originals, but the murals covering the walls of the central building and made out of various jades and jadeites are worth the price of admission (about 5 bucks). A couple of yuan to ring the large bell was also worth doing a couple of times. Don't miss the temple.
The area is filled with shops and touristy stuff like yellow-clad rickshaw pullers and various performing groups as well as boats you can tour up and down the (small canal of the) Quinhuai River. We simply wandered around, bought a few candied chestnuts and a yappy dog toy, and people-watched, but there is plenty of shopping if that turns your crank. I wished for a Chinese guide or a better command of Chinese when we passed the Zhanyuan Gardens and it's adjacent calligraphy shop - I felt that I'd be unable to adequately describe my desires to the shopkeeper, who had a beautiful selection of calligraphy papers, brushes, and inks. Shoulda tried anyway.
Overall it's worth seeing, and while it can be crowded and is certainly touristy, the high points outweigh the low.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.