Summary
I switched to Republic from Monarchy in -225 the same turn I built Michelangelo. I could have done it sooner but decided not to. Four of my cities celebrated immediately. I switched to Democracy in 460. This is one the rare occasions when I switched to Democracy without either Magnetism or Bach. I did lots of prior planning for this and it worked out OK. I had to disband one military unit exploring far away but other than that things were under control.
I kept my taxes and lux higher than I normally do at the expense of my science. I need to make up for this quickly. So far I have managed 1 tech per turn in Democracy and in turn 520 I got my first 2 techs per turn (at the expense of setting taxes to zero).
As usual I put an emphasis on wonder building and have got all the ones I really wanted. Bach has been started and should be done around 600. One dumb mistake I made which delayed growth in my science city was building Copernicus before Shakespeare at a time when my science rate was 10-30%. Science city is currently at size 23 and still has room for a few more citizens before farmland.
Foreign relations have been stellar. I have had no incidents with anyone. I kept monitoring their attitude towards me and gifted them techs as it dropped. I put an early emphasis on exploration and found Russians very early on and blocked their passage into my part of the continent by fortifying a warrior at 48,60 (now a musketeer in a fort). They never challenged that.
I have had limited success, but success nevertheless, guiding rivals to discover useful techs.
Besides my homeland, I have explored and settled most of continent 4 (thanks to some nomads), many little close islands, and have recently ventured into continent 27 where I have 3 size 1 cities. I have deliberately not built any cities on rival's homeland.
-0925 Philosophy -> Construction -> Bridge Building. 8 barbarian horsemen from hut which kill my warrior the next turn.
-0850 Tula and Tamuin founded.
-0800 Hanging Gardens built. Beads to Carthage for 80 establishes the first trade route.
-0775 Silk from Science city for 228 establishes the second route. Construction, Philosophy -> Sioux (1) -> Math.
-0750 Bridge Building -> Monotheism.
-0725 Teayo founded.
-0700 Cempoala founded.
-0675 Gems from captial to Moscow for 90 establishes the third route. Chalco and Tlalmanalco founded.
-0625 Ixtapaluca and Huexotla founded. None settler from hut on continent 4.
-0600 None settler from hut on the other side of continent 4.
-0575 Tepexpan founded. Dezful founded by Nomad on continent 4 as the first offshore city.
-0550 Colossus built. Kish founded on island 32.
-0525 50g from hut. 50g from Russians.
-0500 Zitlaltepec founded.
Status at -500
Population: 0.61M; Cities: 23; Trade routes: 0D3F; Government: Monarchy
Gold: 43; Cost per turn: 0; Total advances: 21; Production: 75MT; 0 polluted tiles
Wonders: Marco, Hanging Gardens, Colossus
Units: 7 Settlers (1 none), 10 Warriors, 2 Archers, 1 Horsemen, 1 Chariot, 4 Triremes, 1 Diplomat, 5 Caravans
Russian: 5 cities, 21 techs
Zulu: 4 cities, 12 techs
Viking: 5 cities, 18 techs
Persian: 4 cities, 18 techs
Carthaginian: 3 cities, 11 techs; War with Sioux
Sioux: 3 cities, 15 techs; War with Carthaginians
-0475 Monotheism -> Medicine. Kharg founded. T7L0S3
-0425 Medicine from hut.
-0400 -> Republic. Advanced tribe founds Shiraz on continent 4. Construction -> Viking (5) -> Republic.
-0375 -> Banking. Rasht founded.
-0350 Zabol founded. Beads to Vikings for 264.
-0325 Zahedan founded. Advanced tribe founds Neyriz in continent 4. Hides to Vikings for 208.
-0275 Banking -> University. Bridge Building -> Viking -> University. University, Republic -> Russian -> 150g.
-0250 -> Astronomy. Seafaring from hut. Republic, University, Seafaring -> Persian(3). Revolution started.
-0225 Michelangelo built. Russian -> 50g. Republic established. T8L2S0. None settler and Warrior Code from hut. Shush founded.
-0200 Hides to Vikings for 272. Laar founded. 4 cities celebrate.
-0175 Chiauhtia and Anzali founded. T6L4S0
-0150 Republic, University -> Sioux(0) -> Astronomy
-0125 Republic, University, Trade, Warrior Code -> Zulu -> Engineering -> Persian & Russian. Chemistry and Crusader from huts. Gheshm founded.
-0100 -> Sanitation. First infrastructure built. Science city and Capital reach size 8.
-0075 Hides from Science city to Viking Hladir establishes its second route for 640 (capped). T5L4S1. Astronomy -> Persian -> maps.
-0050 Sanitation -> Theory of Gravity. First domestic offshore routes established for 78, 114.
-0025 T4L5S1
+0001 Hides from Science city to Viking Kaupang establishes its third route for 661 (capped). Four barbarian horsemen from hut kill my warrior the next turn. 9 techs to Sioux to reduce research cost.
Status at +0001
Population: 2.9M; Cities: 34; Trade routes: 4D8F; Government: Republic
Gold: 424; Cost per turn: 7; Total advances: 32; Production: 148MT; 0 polluted tiles
Wonders: Marco, Hanging Gardens, Colossus, Michelangelo
Units: 14 Settlers (2 none), 26 Warriors, 2 Archers, 1 Horsemen, 1 Chariot, 1 Crusader, 7 Triremes, 1 Diplomat, 25 Caravans
Russian: 6 cities, 24 techs
Zulu: 7 cities, 18 techs
Viking: 5 cities, 22 techs
Persian: 5 cities, 30 techs
Carthaginian: 3 cities, 13 techs; War with Sioux
Sioux: 3 cities, 27 techs; War with Carthaginians
+0020 Theory of Gravity -> Economics. Domestic offshore Gems for 402. None settler from hut.
+0040 Zulu build Pyramids. 8 barbarian horsemen from hut kill my warrior the next turn. Hides to Sioux for 232. Hides to Vikings for 248. Spahan founded.
+0060 Economics -> Invention. Copernicus built. Salt to Vikings for 96. Beads to Sioux for 280. Shushtar founded.
+0080 Chapultepec founded.
+0100 Hides to Vikings for 312. Feudalism from hut. Feudalism, Chemistry, Seafaring, Sanitation -> Russian (3) -> maps. Tech bombed Sioux.
+0140 Vikings build Great Library. Navigation from hut. Navigation -> Persian.
+0160 Shakespeare built. Invention -> Gunpowder. Invention -> Russian, Persian, Sioux. Silk to Carthaginians for 90. Beads to Vikings for 156. Tlapanaloya founded. T3L4S3
+0180 Domestic offshore Wine for 180. T5L4S1
+0200 Hides to Vikings for 84.
+0220 Salt to Carthaginians for 92. Domestic offshore wool for 80. Babol and fasaa founded. Nomad from hut.
+0240 Gunpowder -> Metallurgy. Paasaargaad founded.
+0260 Leo built. Six barbarian horsemen from hut which all die attacking my musketeer. T1L4S5
+0280 First library built in science city. Silver to Carthage for 100. T6L4S0
+0300 Advanced tribe founds Amol. Deliveries to Vikings for 172, 265, 64. Tonb founded. T3L4S3
+0320 Metallurgy -> Explosives. Brujerd, Lahijaan, and Naayin founded.
+0340 Deliveries to Zulu for 128. 50g+25g from hut.
+0360 Russians build Sun Tzu. Deliveries to Vikings for 132, 216, 255.
+0380 Persians build King Richard's. Explosives -> Physics. Abadan and Miyaanrud founded.
+0400 50g from hut. Wine to Zulu for 240. Bushehr founded. T0L4S6
+0420 Physics -> Democracy. Cloth to Sioux for 140. Two barbarian knights from polar hut which freeze to death the next turn. T2L4S4
+0440 Deliveries to Zulu for 280. Rudsar founded. T4L4S2.
+0460 Democracy -> Theology. Democracy established. Deliveries to Zulu for 120, 94. Tequixquiac, Kerman, Sirjaan, and Dashtestaan founded. T1L2S7
+0480 Theology -> Atomic Theory. Newton built. Saari and Khorramabad founded. Domestic offshore Beads for 64. Deliveries to Vikings for 330, 132, 106.
+0500 Atomic Theory -> Magnetism. Magellan built. Domestic offshore Spice for 105. Wine to Vikings for 290. T0L2S8
Status at +0500
Population: 11.6M; Cities: 56; Trade routes: 14D32F; Government: Democracy
Gold: 105; Cost per turn: 56; Total advances: 44; Production: 259MT; 0 polluted tiles
Wonders: Marco, Hanging Gardens, Colossus, Michelangelo, Copernicus, Shakespeare, Leo, Newton, Magellan
Units: 26 Engineers (4 none), 18 Musketeers, 2 Horsemen, 10 Caravels, 2 Diplomats, 16 Caravans, 1 explorer
Russian: 6 cities, 39 techs; Sun Tzu
Zulu: 7 cities, 21 techs; Pyramids
Viking: 6 cities, 37 techs; Great Library
Persian: 5 cities, 36 techs; King Richard's
Carthaginian: 3 cities, 15 techs; War with Sioux
Sioux: 4 cities, 44 techs; War with Carthaginians