Where the mage apprentices practice their spell-casting. Renald Viernis is the Proctor of the practice rooms, and can be found casting spells most of the day, along with a Mage Apprentice. The stairs in the northeast corner lead up to the upper level.
The main floor contains two spell target boards on the right side of the room, and an additional target in the corner on the left side. There are a several containers in the room; four barrels - two in the northeast corner and two on the south wall, two sacks and a chests in the northeast corner, a desk and another chest beside the stairs, and a chest of drawers on the south wall all contain clutter. The two sacks do not respawn, but the other containers do.
Practice Rooms Upper Level
There are four target boards on the upper floor, with one of them in a corner. Apprentices practice their spells here most of the day.
There is nothing of much note on the upper level, with two clutter barrels, four clutter sacks, and a desk with the same contents scattered around the room. A small stand with a plate that holds two apples and a pear is near the door for mages on break. A table surrounded by two chairs on the east wall has a plate with two apples and a loaf of bread on top of it. The two barrels and desk respawn, but the four sacks do not.
Elder Scrolls Wikia entry on this location can be found here.