If you are wondering what to do with the kids to enjoy some outdoor fun in winter in Yokohama, this "Art Rink" outdoor skating rink is a fun option.
The whole red brick warehouse area offers good shopping options as well as dining choices like breakfast at the Australian import breakfast favorite Bills. The concept of this "art-rink" is that it should be a display area for local artists, but when we went there on January 3rd during the winter holiday, there was no art on display anywhere. Regardless, it was a fun, active break and a good distracting alternative to all the other indoor activity that is usually done in the colder months that makes kids a bit bored.
Although it is actually not a very big rink and gets quite busy (ice-skaters may get frustrated) if you don't mind moving around at a slow pace with the crowd, it is lots of fun and doesn't cost too much. It is ¥500 a person and ¥400 for kids in elementary school (12 years and under), then there is a ¥500 rental charge for the skates. They have lots of sizes for kids through adults, it helps to know your shoe size in centimeters (Japanese shoes are sized this way) before you go and choose which rental skate you need. For adults, there were two types- both with heels for figure skating, but the two-tone version are wider and larger men's versions. If you have feet larger than 28 cm you may be out of luck for a rental pair.
On Saturdays and holidays (including the "oshogatsu" school holidays) the rink is open from 11 am to 10 pm. On weekdays it is open from 13:00-22:00. It is only open in the winter months from December 7th to February 23rd. All skaters must wear gloves (you can also buy them at the counter if you don't have any), payment is by cash only and the rink is closed in the event of rain or bad weather.
I would recommend getting there early when it opens to enjoy an hour of skating before the crowds really pile on the ice about an hour after opening. The quality of the ice also really getting chopped up quickly with so many skaters. We were there from 11-12:30 on a busy day and there was no break to clean up the ice that we saw. There are staff on the ice to try to keep people skating in an orderly fashion and not sitting on the walls, skating against the current or acting otherwise disorderly.