As a side note. The french potter Bernard Palissy, (16th century), did some grotto work that is amazing. He was also a very strange and curious fellow. Try this link to find out more: http://www.strangescience.net/palissy.htm
Steve

Thank you both for your prompt responses.
Zeuspaul, great points! Had not thought about the masses of stone to regulate temps. Would also eliminate my concern of how to cement rock to plastic. Could you please tell me what you would use as a "form" to hold the rocks in an arched position till cement has dried? The small pool inside was what I too had in mind. Am still learning about all this irrigation "stuff", & will check out the sprayer you suggested.
Steve, thanks for the link. Am going to check it out rite now. Hope there are some photos of his grottos.
Thanks again for your help...mary

Could you please tell me what you would use as a "form" to hold the rocks in an arched position till cement has dried?

You could try the Keystone retaining wall blocks available at Home Depot. They have a wedge shape and would hold themselves in an arch position. You could then pour mortar in the gaps to help hold the thing together. I have considered such a *grotto* dug into a hillside as a possible bobcat den.

For the arch to hold itself up you would have to provide some lateral support. If the arch starts below the ground level the earth would provide the lateral support. If the arch starts above the ground you would need an extra thickness of heavy stone to provide the lateral support.

Zeuspaul...thank you again for your response & suggestions. I'll check out the products you've mentioned, although I should probably refrain from explaining what I'm trying to build.
I envy the fact you have a slope in your yard to work with! This grotto/cave-thing would certainly look nicer blended into the hillside. (Though I'm sure the bobcats aren't interested in that!)
You've been a great help. Thanks! mary

A grotto, how cool. As a teen I use to read gothic romances and there was always a grotto somewhere on the estate grounds. Sounds like a project involving stone that I might be able to manage for my shade garden. I can see the dh rolling his eyes already. Just a funky little cave dripping water into a shallow chiseled out rock for the critters.

Exactly Jill!!! Water is so scarce here & all the poor critters NEED to drink. The grotto here is a second thought to a St. Francis fountain that I plunged into w/out research & ended up w/a pile of lava rock that the water just ran under. Still, the birds & lizards loved it. Have many bird baths, but those on-the-ground little guys need a slurp too. And the shade & coolness is much appreciated by all.
Perhaps you could avoid DH's eye rolling by explaining how romantic it could be? Let me know how that one goes over! :)
Thanks for the encouragement Jill, & keep me posted on your adventures-in-grotto-building...mary

There is an "interesting" grotto made from stone, earth and green ground covers at:

http://www.doc.ic.ac.uk/~reuben/UK/wardour/grotto.jpg

You'd have to find upright stones but they are plent;yful if you have a way to haul them in from one of the canyons. I think the creeper covering blended with wild flowers would be beautiful.
I live in UT also. 40 mi. west of Salt Lake City.

My husband surprised me tonight with an early Christmas present - well actually he was told it was going to arrive in 3 weeks so he thought it would be perfect timing for Christmas but they shipped way ahead of schedule... He was more excited than me so I got to open it early... I had been talking about building a grotto or a Mary's Garden in a corner in our backyard. He got me a 34-inch tall sculpture of the Madonna. I've spent the night looking for ideas for a grotto and garden. I've come across this site and delightfully found this thread that suits my very needs. Thank you so much for a very informative thread. I can't wait to start on my project.

this one might provide some inspiration...installed at Ridgeview Hospital in Waconia, MN.
GH

Here is a link that might be useful: Healing Garden Grotto

zeuspaul - could you go into further detail (as if you are talking to a 7 year old) about keystone, and archbuilding????
I know the stones you are talking about at Home Depot. This post got me to thinking about grottos again, something I wanted but didn't know how to do. Grottos range from room sized caves to a niche in a wall. The grotto the poster is talking about seems to be a smaller version to cup the water?

It must have been the first post on this topic that started me thinking about making a grotto. I had seen an book at a bookstore that had detailed instructions for various garden projects. One of them was a grotto. From what I remembered the grotto was formed with chicken wire and cement. I wish I had purchased the book but I was just browsing at the time. This post started me on an internet search for info and pictures of grottos. I thought maybe I would work with fieldstone and cement. During the demolition phase of our addition I collected a lot of stone. When I found some pieces of granite I decided to do a quick setup of grotto.

I dug a large flower pot sized hole in the ground and lined it with pond liner material. I purchase a small pump and placed this in the bottom with water. Then I put mesh over the top (level with the ground) and small stones to cover this completely. I used the granite to form a ring (open at the front). Then placed a large flat stone on top. I stacked some round flat stones inside and the water ran down over these and back into the hole. The fern was in a small flower pot and stayed pretty happy.

This is not the grotto I originally thought of but due to priorities of our addition project seemed to work just fine. I might attempt something more involved next summer with cement or hypertufa.

Here is a link that might be useful: my version of a grotto

very imaginative - definitely grotto

Look at this grotto:

http://lndyrss.tripod.com/TheGrotto.html

That is a gorgeous grotto! Thanks for posting the pic!

This google image search has quite a few pictures of various grottos, sevral pages worth.

Here is a link that might be useful: grotto search

We did a very simple one last year. We are thinking of adding a water feature to it. Not exactly a "grotto" but it works for us.
{{gwi:289204}}
Mary Lu

I like your grotto -- very nice! Are the stones place dry or did you cement them?

Hi all...well, it's 5 years since I first posted this question & finally have my grotto built. Sorry, no digital camera, so no pictures, but I can now tell you how I solved some problems. I bent a sheet of bender board & held it in place w/large rocks on the sides. Then cemented lava rocks to it. Problem #2 was getting the rocks to "stick" to the inside sides & top, where the most curve was. I had tried just about everything when I thought about trying "fake rock". Got a couple cans of "Great Stuff" insulation & sprayed glops right on the bender board. Actually turned out better than I had thought, because they started to hang down like fat icicles. Some fell off completely, but were easy to glue on after they dried. Painted them to match the lava rock & that's it. Although I originally wanted it to drip water, I needed to forgo that. I lost my 2 beloved birds late last year & built the grotto over their graves. I hope this helps someone else.