This patio is one of the most interesting that I have ever done. What made it so was that the water table in the area is very high so we could not use a conventional foundation made of compacted aggregate. What we did instead was installed a permeable foundation made of 40mm limestone and heavy reinforced it with geo grid and geo textile. You would not know of the extra effort that went into making this beautiful feature solid just form looking at it, but it gives me peace of mind knowing that the patio will stay where its supposed as the years go by. We used River Rock in Tofino Grey from Expocrete with a 4x8 Holland soldier course on the outside.