The City of Dalaran is the center of Northrend where both Horde and Alliance are able to roam and go about their business in peace. Below that is the underbelly of the City, the Dalaran Sewers. Here is where mostly goblins dwell. It is the slums of Dalaran but is also where the Northrend arena map is set.
The map has many unique features not like any other arena map. The layout itself begins with you in a drainage pipe on the end of the map somewhat high above the ground. When the match starts you will either jump out of the pipe or be blasted out after a certain amount of time. Once on the ground, you will notice the center of the map is a square shaped raised part with stairs right where you drop down and 2 sets of boxes on either side. The map is a mirror image for your opponents as well. The last big thing to note is the large waterfall that will drop down in the very middle of the raised platform every once in a while. This is treated as a line-of-sight object so be ready for it. If you are near it when it drops you will be knocked back.
Using the boxes as your base of operations for those who need a line-of-sight object is perfect. Healers will often want to hug these only coming out to cast quickly and then duck back behind them. When up against a heavy ranged group, even your dps will not want to go far from these boxes as getting caught out in the open in a burst moment can prove fatal.
Be aware of the center raised parts edges as to not fall off accidentally or get knocked off by an elemental shaman during a critical moment. Even dropping down off the side will give you an LOS moment in a critical situation. But being down on the bottom while a caster is on the edge gives them free range of you and can be another fatal move if they catch you in a bad spot. All of these factors will need to be considered by you and your team in order to have control of the match. That is the key to most of these arena matches, not only knowing your strengths and weaknesses vs your opponents but also the arena maps. Sometimes a game comes down to a few HPs, every moment and extra strategy counts!