PtW, open class, trying for a 20k victory.
First the important stats: 124 hours played, submitted with 8 hours to spare
Now I normally make sure to have at least one moment of monumental stupidity in my xOTM, and in this game my mistake was winning! No, not an accidental domination, it's dumber than that... but before I relive the agony, I'll recap the glory years.
Ancient era:
I thought my AA was pretty competitive, using my capital for the 20k attempt. I didn't lose any big builds, although I had to delay the completion of the Great Library for several turns while I researched Republic and then waited out 4 turns of anarchy. Finishing the Glibrary initiated my golden age, which would end the same turn I entered the medieval. I ended the AA in 30ad with palace, temple, Pyramids, library, Glibrary and Gardens, for 1123 culture (33cpt).
Medieval era:
This started with a dow from Rome, so I pressed my immortals into late service, eventually reducing Caesar to a single jungle city, where he spent the rest of the game (thanks to Moth for describing this technique in the AA spoilers). Japan wouldn't declare until I extorted some cities from them and then failed a spying mission. Of course, that's because they were one of the weediest AI empires I've ever seen, for no good reason that I can think of.
I used my first great leader, earned against Rome, to build an army of immortals. My second, earned in the dying moments of the Japanese campaign, built Forbidden Palace in Kyoto. I believe the decision to forego a free wonder in the 20k city, in favour of a good second core, enabled me to keep my research so relentless in the later game.
I ended the medieval in 1210ad with cathedral, colosseum, the Epic, Michaelangelo, university, Copernicus, Shakespeare and Newton, for 6570 culture (82cpt).
Industrial era:
It was only at the start of the industrial that I realised Caesar was probably slowly building defensive units in his 1-tile town. I could use cannon to check whether he had more than one, then kill off the excess with my elite immortals. This is how I got my third leader. Up to this point, I had considered trying the whole 20k without any leader rushing, but presented with such unexpected bounty, I cracked and rushed Suffrage.
The rest of the era went to the usual plan, cash rushing industrial improvements as soon as they became available, and building the industrial wonders before the AI even had sight of their techs. The 20k city maxed out at 102spt net at size 21; over the hundred mark is so important, and it was just enough to absorb a bit of pollution every so often.
The industrial era ended in 1510ad, having built all industrial great and small wonders, for 11607 culture at 97cpt.
Modern era:
In 1580, the Ottomans dowed on me - the Sipahis' ongoing success against the feeble Celts must have gone to Osman's head. I hadn't planned on ever setting foot on Large Continent, but the opportunity to annex some luxury sources was what persuaded me to go and put Osman in his place. Besides, with nothing left to build in my core cities, I had started stockpiling bombers.
A couple of naval builds later, I had two tank armies liberating the first Celtic town from Ottoman oppression, with Brennus as my ally. I wasn't defending his towns of course, just waiting for Osman to capture them, and then claiming them for myself. This dance wound down in the mid 18th century with both Celts and Ottomans reduced to city-states.
It was while working on the Cure that I get my fourth leader from the much-abused Romans. I rushed Cure and finished up the last wonders, Bomb and SDI in 1772. At 135cpt, victory was due in 1794ad, but sleep deprivation had made me careless!
The mistake:
When the Ottomans were clearly beaten, I had again found myself with nothing to build in my core cities, so I started doing SS parts for fun. What I didn't realise was that when you build the final part, you can't cancel the SS screen, as you would if you had got there using F10. In 1780ad, the SS Casing finished and I was forced to launch! All my meticulously-planned builds orders and research schedules squandered! Ah well, I'll have to wait for another game to claim my first 20k victory...
General notes:
Firaxis score 5005 (happies > territory), Jason score 7279, national culture 88412, capital's culture 19113.
This was supposed to be a quick game to buy me a bit more breathing space in my xOTM schedule, but it soon turned into a milking session. I had hit the luxury slider early and hard in order to keep the 20k city ticking over, with the result that the rest of my empire was scoring unusually highly. Indeed, I was secretly hoping for a better Jason score, but restricting myself to the smaller continent (until the very end) was always going to be a limiting factor, not least because Osman had the foodiest land on the map. I also wasn't very aggressive in clearing the jungles.
I don't understand why the AI were so weak in this game. Japan had only built four or five towns by the mid-medieval when I started on them, and they weren't properly roaded up. In tech terms, the AI still had to do Radio to reach Modern, while I only needed Stealth and Advanced Flight to reach Future.
Now that i thought i would get my first prize with a 175? 20K finish 
As always i did the mistake to cripple the home continent civs so bad that a leader factory was virtually impossible. I could only rush 2 wonders. So stupid 
Well, next time ill try to remember that 20k in PTW means that i must produce GL
Because I'm an idiot and didn't think of it. Thank you. I've just spent a whole minute doing that and squeeked in a submission under the wire. I'm afraid I won't be able to get a writeup done though - at the moment I'm just work-eat-sleep rinse/repeat 
If they happen a lot then we need to help you sort out the problem. But in an isolated instance, and as long as you didn't take advantage of it to play the game differently with prior knowledge, your game will be included.
