Well, it's finally finished. Thanks to the people who pointed me toward architectural drawings, and thanks to the people who made Overseer (and fixed my silly version incompatibility problem so I could use it). Also thanks to the ancient Greeks, who had no clue their architectural genius was going to be shamelessly copied by booze-soaked beards on legs.
Overview of the whole thing. The colored rocks are supposed to be a rainbow but that didn't quite work out... ah, well. In the real Parthenon, the area was covered by carvings, and archeologists figure that the sculptures used to be painted in bright colors when they were new.

View of the treasure room, where the priests used to put sacrifices and donations and things. Naturally, I turned it into the fort's artifact room.

View of the main chamber. This is where the statue of Athena would have stood. Since the statue was much larger than a single dwarf-made marble statue, I have yet to put anything here. The space is 13 tiles wide. Any ideas?

The Building:
Dimensions: 134x71x40, built underground from Z-level 53 to 93
Materials: Approximately 60,000 blocks of white stone, almost exclusively marble, smoothed into blocks before construction.
Decoration: 704 masterwork marble statues.
The Dwarven Parthenon was built underground. Much of the scaffolding did not have to be constructed, but was mined out before building and left in place to serve as scaffolding, speeding up construction significantly.
A lot of the building is actually hollow--inside the walls, under the foundation, in the pillars, etc. More room for the builders and scaffolding, less stone needed.
I planned out the building and its dimensions before beginning construction, using lots of photos of the real Parthenon and, ironically, Microsoft Paint, since it has grid and ruler features.
The Fortress:
Age: 39 years
Population: 70
Casualties Suffered During Construction: 79
Forgotten Beasts Killed: 25
Legendary Masons Alive: 32
Cheats Used:
DFHack--Cleanmap and Autodestroy for FPS management
Tiletypes--Used to create more marble to mine out for the building. No part of the building was actually created with tiletypes; each block was mined and smoothed by dwarves, but I realized that it would be impossible to find enough marble on a single embark, so to avoid a multicolored Parthenon I resorted to refilling existing marble layers for dwarves to mine out.
I got lucky with an unusually peaceful area. I left invaders on, but because the area has no neighboring civilizations other than dwarves, the only combat came from the local giant capybara population and the forgotten beasts which occasionally came to nose about the fortress. One beast killed several marksdwarves with a deadly syndrome causing blisters that affected every. single. organ. Seriously, they even had blisters on their spleens. (And lungs, which caused them to suffocate.) One beast was made of periclase, another of ice. Thank goodness for the steel-battleaxe squad.
So there it is. I think it looks nice, but needs more magma.