Since I did a page on the "Me" cave I figure I probably ought to discuss the Grove as well. The grove is the Spirit Walk's analogue to the Shadow Journey's cave in many ways (the difference between the two techniques is outlined in Walk/Journey), but its original purpose was quite different. This part of my path evolved a bit over the years, so perhaps I ought to start chronologically.
Though I started studying parts of "the occult" many years before this, by the time I was 15 I no longer felt a connection to (or particularly welcome in) the religion I grew up with, namely the Catholic Church. I groped about for a bit before finding a copy of Scott Cunningham's Wicca: A Guide for the Solitary Practitioner. I latched on to that with both hands (feet and teeth as well) and honestly got as silly as any teenager stumbling into these things. Since there was no way I wanted to risk my family discovering my "heresy" I had to come up with a way to perform my rituals without my parents finding out.
Astral space, which I'd played with a bit before this, was the perfect answer. So I built myself a circle of trees in journey space, put up an altar, and proceeded to do my work there. Several years later I did my first journeying in a kind of guided meditation. I was told to find a place to enter the dream space, and the grove floated up to my mind. Since then my path out on a Spirit Walk has passed through the grove.
While the grove isn't nearly as complex as the "me" cave, it's honestly just as important to my path. One of the main reasons for this is simple psychology - it taught me that tools aren't necessarily needed to accomplish a goal if the will is focused properly. It sharpened my ability to work thoughtform energy into the tools I thought I needed. Another reason is that it gives me a starting point and a staging area before I go out on a walk, which effectively prevents me from "forgetting my moleskin," to extend the hiking analogy a bit. Last, it gives me a place where I'm quite comfortable working, that I can go to if I find myself needing to work for some reason and am completely unprepared - it's a portable circle. It may not be as effective as techniques which require spatial components (i.e., moving around a room), but I've found that if I'm really that desperate I can force the grove to share the same physical space that I'm in, effectively giving me at least a superficial protection which can then be built on.
And since I'm so fond of adding disclaimers and warnings to these pages, I would like to point out that attempting to overlay astral space on a physical location is not something to try for the first time in an emergency situation. While the adrenaline may be useful in giving you the boost you need to focus will, it's really a mindbending thing to try to visualize, and draining as hell to maintain, and generally is a bad idea unless you're stuck. Conventional methods of creating sacred space will typically be more effective regardless of the time absorbed in casting a circle the usual way. Bringing the grove, or any other type of astral space, into reality is only going to be as useful as the amount of energy you've put into it, so if you haven't used it a good deal it's really not worth it. And, as I've said before, don't try this for the first (or even second!) time without someone else there capable of keeping you in one piece.