Neronvain and Chuth's stronghold from Rise of Tiamat. Neronvain is the green wyrmspeaker, so I've very much gone for a green theme in her rooms.
I think I've followed the description in the module pretty closely, except that I've put in more light. I've used a glowing green moss to give the place a dim ambience, and I've put some candles in sconses around in the inhabited areas. I've done this because no-one likes to live in the dark, and it looks cool.
Note that there is an "underwater" level where the hidden, subaquatic tunnel is shown.