The Marketplatz at Christmas time (usually Dec 1-24) will house the traditional German Christmas market. Trier is one of the largest ones that I went to during my time in Germany and one of the best. These Kristkindle Markets as they are called are very crowded and sometimes incredibly cold as they are entirely outside, but well worth every hardship you endure while there. Have Gluhwhine (pronounced Glue-vine) at one of the many, many stands, and you can keep the mug it comes in or give it back to one of the stands to get a portion of your money back. Gluhwine is warm spiced wine and has liquor in it but they also have hot chocolate if you don't want the liquor. There are stands here to purchase presents and to purchase the traditional German Christmas decorations such as smokers, nutcrackers, and ornaments. Trier also had real pine wreaths and garland in the farmers area that I purchased every year and I have never found a real pine that smelled as wonderful as these. There are also a handful of children rides here, something I didn't see at many other markets. The Trier market spans well outside of the main market square now and over into the square where the Dom Cathedral is. The entire area, including where there are no booths is decorated with lights and decorations. By far my favorite time of year and thing to do while in Germany was the Christmas markets, and we went to this one each year, sometimes twice if family is in town.