Asgard is small, a disk rather than a globe. You'd recognize her by the large golden castle that sits at her center and the Birost observatory on her edge, where the Gatekeeper Heimdall stands watch over the Nine.

[Loki gets an almost wistful look in his eyes.]

But unless you're from the past in relation to me, there will be no 'coming across it.' She was destroyed shortly before I awoke here.