We have almost finished with Phase One of the patio project:  the actual
patio.  This patio is approximately 1200' square with a 45' x 4' pergola
"run" (8' pergola yet to be built) that will end in a raised circular
patio made of fieldstone and flagstone. In

this
photo, you can see the end of the pergola run (gray crushed stone with brick
on either side) and the black plastic edging represents where the circular patio
will be constructed.

Planned is a watergarden with a stream/bog/biofilter, that will run from a
spring erupting  between the pergola run and the bed behind. We are
planning to dig this area down a bit and provide a french drain to
reduce/eliminate runoff into the stream and pond from neighboring beds. It will
run down and to the right over a single spill stone which will be towards the
bottom right of the picture.  (There's a pile of gray crushed rock there
now.)  There will be a stacked stone wall (dry or mortared, not sure) where
you see one now (that one is just temporary stone storage and visualization
aid). The water will trickle into a small pond with a false bottom (two toddlers
at home).  The pond will be just to the left and below the hydrangea that
you see at the right bottom corner of the picture. Behind the pond and under the
spill stone will be a small grotto for ferns and sound amplification. 
Closer to the rounded half moon bricks at the end of the brick path will be a
large boggy area surrounding the circular patio.  There will also be a
short gravelly, beachy area leading into the water of the pond and stepping
stones going from the brick path through the bog and around the circular
patio. 

The patio is flagstone, black slate, and brick softset with a 4-6" base
of crushed rock and a 1" bed of sand.  We have had no drainage
problems on the patio (it's been in a year, through Isabel, and this wet, wet
summer with no standing water whatsoever).  The patio/photo is  facing
south. We are Zone 7b with a somewhat warmer (8-8b) microclimate in our yard.
There will be no fish in the pond. Overhanging branches, leaf and pecan fall are
a problem we are willing to deal with. The basic subsoil is clay, although most
of our soil is rich, black and crawling with earthworms.  We do contend
with voles and moles. All the work will be DIY.

We will be posting to the Ponds Forum with similar questions, but with a
focus more on biofiltering, liner, etc.  In this forum, we are looking for
advice regarding the stonework, retaining walls, foundations, etc. Obviously, we
will have to have a very detailed, well thought out plan before we begin, as the
circular patio will require a concrete, reinforced foundation and the pond liner
will need to be worked into the foundation to prevent leaks from the pond. 
We are planning to have the liner completely concealed within stonework, gravel
and bog.  We are looking for advice, considerations, suggestions and
questions that we should be asking ourselves before we undertake this
venture.  We won't be breaking ground for this project until next spring,
due to other projects underway, the need to plan carefully, and BUDGET, so there
is plenty of time for bantering ideas around.  :)  No eggshell mulch
here. Other photos provided at the link below

Thanks in advance for any input.  Critique away!