The Da is the opening in the Zollikon Seminars:

In the philosophical tradition, the term "Dasein" means presence-at-hand, existence. In this sense, one speaks, for instance, of proofs of God's existence. However, Da-sein is understood differently in Being and Time. To begin with, French existentialists alos failed to pay attention to it. That is why they translated Da-sein in Being and Time as être-lá, which mean being here [spatial adverb] and not there [pronoun; e.g. there is]. The Da in Being and Time does not mean a statement of place for a being, but rather it should designate the openness where beings can be present for the human being, and the human being also for himself. The Da of [Dasein's] being distinguishes the humanness of the human being.
P. 120

And thus also the clearing.

How is the "there" [da] then determined as "the open"? This openness has the character of space as well. Spatiality [Räumlichkeit] belongs to the clearing [Lichtung]--to the open in which we, as existing beings, [naturally] sojourn in such a way that we are not expressly related to space as space in any way.

The being-in-space of a untensil cannot be reduced to the spatiality of "being-there" (Da-sein). Yet, the reverse is impossible as well. Both spatiality and temporality belong to the clearing. Space and time belong together, but one does not know how. Now how about consciousness? To stand in the clearing does not mean that the human being stands in the light like a pole does. Rather, human Da-sein (being-there) is sojourning [sich aufhalten] in the clearing and "concerns itself with" [beschäftigt mit] things.
P. 144

And where is it when it's not sojourning in the clearing?  ¶ 10:35 PM