We recently set up an outdoor pond/enclosure for our RES. It's a 60 gallon pond liner that we put in-ground. He's got hiding spots under water and a big basking area. He does not come out of the pond unless we take him out- he is still too small. He does like to wander around the rocks, supervised of course.
Here's a pic from when we first got it set up...
Here's a more recent pic- changed up the basking area and check out the hasta growth! It's providing some natural shade- love it....
I do want to get some type of waterfall/filter going. Not sure how we are going to do that but it's definitely on the list!