Outside the ruins of Saarthal are the trappings of an archaeological dig- and no people, curiously. This leaves you free to root around and, in addition to a remarkable quantity of food probably intended to supply the diggers, you can also turn up a considerable amount of treasure from some burial urns and some ore from a silver vein in the main pit itself.
While you will have ideally reached this point before Tolfdir and the other apprentices, you may have reached Saarthal after the aged mage, in which case he will actually wait for you to finish rummaging around. If your time is short, you can use the Wait function to advance time until he and Brelyna are present- the other apprentices, oddly, don't seem to show up at first.
Brelyna, the relatively soft-spoken dunmer, is enthusiastic about the digsite, but has little to say. If you like, you can talk to Tolfdir about Saarthal while you wait for J'zargo and Onmund. The teacher explains that the significance of Saarthal is related to the raw quantity of seals present in the ruins, which is very unusual. His enthusiasm about the ruin is, he explains, due to the mystery of the place, as there is no clue as to what can be found here. He is also hoping that if anything happens, the danger inherent to magic will become more evident to the apprentices, who he considers overenthusiastic and incautious.
Cautioning you to stay close by just in case, Tolfdir leads the way into the ruins. Don't worry if nobody other than Brelyna has shown up yet- the others will appear on the inside of the door at the same time as you.
As you descend the scaffolding, your teacher begins to explain that Saarthal was both the largest and one of the earliest Nord settlements in Skyrim. He explains that the settlement was sacked by elves during the Night of Tears, and nobody's really sure what happened to it after that. Tolfdir enthuses again about the opportunity to explore and discover, which brings you all to the bottom of the ramp and your first footsteps within the ruins themselves.
Turning to you, Tolfdir asks you if you're ready- ask him what to do and he'll instruct you to aid the College member already present, who is looking and digging about independently. Brelyna, he sets to locating and identifying any warding magics she runs across.
