The grid is accessible via hypergrid at <7000, 7000> on port 8002, i.e. using the following URI without the http:// prefix:
You can simply open the map, enter or cut and paste this URI in the search box, and you will arrive in the region Annwfn on Ocean Grid. You can teleport to it in the normal way that you would teleport to a region on your home grid (e.g. OSGrid, Ocean Grid etc), providing that hypergrid is enabled in the region in which you are currently located.
Hypergrid to Other Grids
Hypergrid teleports are now very much more reliable in the past, although this will depend on the reliability of the server you are visiting. Note the security information on the OpenSim site.
There is a stargate on Annwfn containing hypergrid links to major destinations. These can be found widely in many grids. Alternatively, check out TheHyperGates.com, OpenSimWorld or Hyperica and they will do all the hard work for you, just like a SLurl.
Don't get lost!
Re-logging will return you home, if for some reason Ctrl+Shift+H (Cmd+Shift+H on a Mac) isn't working. These days, you shouldn't be stuck anywhere for long.