One of the factors that makes Civilization probably the most popular computer game of all time is that it is different each time you play it, and that even the most jaded players can alter the game parameters to suit themselves. The addition of the Fantastic Worlds supplement increases the number of slots available for user-defined technologies and units: though this is intended to allow new units for exotic scenarios (dragons etc), I have taken advantage of this to add to the standard units available in "normal" games, plus alterations to the tech tree and certain Wonders of the World (most notably the Pyramids) and I have prepared a file called PYRAMIDS.ZIP (a 611KB download) which can be copied into your Civilization directory and unpacked (using pkunzip or winzip, eg pkunzip -do pyramids.zip) to give new RULES.TXT and UNITS.BMP files, and new sound effects in the Sound subdirectory for the new units (I suggest you rename your original RULES.TXT and UNITS.GIF or UNITS.BMP files first as backups).
These changes will be accurately reported in the Civilopedia if you delete or rename the GET_INFO.EXE file in the Pedia directory (this disables the standard Civiopedia entries which will no longer match the changes).
Note for Multiplayer users: the latest version of Civilization ("Ultimate Civilization II Classic Collection" or "Multiplayer Gold"), with multiplayer support, requires modified version of certain files. Equivalent modifications are included here in another zip-compressed file, P_PATCH.ZIP (42KB). First, apply the Upgrade 1.2 patch (available from the Microprose Updates page) to fix various bugs in the game, THEN unpack Pyramids.zip, THEN unpack P_Patch.zip to update these files. This applies even to single-player games with this version. The more flexible Civilopedia provided with this version need NOT be disabled, but will give incorrect descriptions in some cases (though the basic powers of units and wonders will be correctly listed).
There follows a summary of the changes, under three headings: alterations to existing technologies and units, new technologies, and new units (some of these changes have been borrowed from Steve Strayer's "fascist patch": the fascist govenment type, the Stormtroopers unit, increased unit support under Communism, the reversal of Gunpowder and Metallurgy and the abilities of the Knights and Longbowmen units).
Alterations
The Pyramids are the most famous of all the ancient Wonders, but their power in Civ2 is fairly minor: a free granary in each city (which can cause problems if city growth exceeds the ability to control unrest). In Civ1, the Pyramids allow switching to any government type. The reasons given are that the Egyptians must have been very good at organising and feeding such a large workforce. I think this is irrelevant: the important point is that the Pyramids WERE built, and the Egyptians then went on to build many more large monuments - they were obviously very good at carrying out major construction projects. I have therefore transferred the power of King Richard's Crusade to the Pyramids (until Industrialisation).
The original Pyramids power, free granaries, has been transferred to a new Wonder, the Temple of Artemis at Ephesus (actually one of the original Seven Wonders of the World, though different historians had different lists). This now expires with Refrigeration (ancient fertility goddesses don't feature highly in modern agriculture). At 150 shields, equivalent to two and a half granaries, this is now the cheapest Wonder.
The expiry point for the Great Library has been changed from Electricity to Espionage, as this seems more appropriate: the international gathering of knowledge ceases as nations become more paranoid about security. To prevent the Great Library remaining active too long, I've significantly increased the priority for computer civs to research Espionage and the techs that lead to it (Communism and Democracy).
Sun Tzu's War Academy no longer expires, making it rather more useful. Many of the basic theories of warfare have stood the test of time (ask Norman Schwarzkopf...).
The expiry point of the Lighthouse has been changed from Magnetism to Steam Engine, allowing fast veteran Frigates and Galleons.
The positions of Gunpowder and Metallurgy have been swapped, with Gunpowder renamed as Firearms: historically, cannons came before muskets.
Metallurgy replaces Iron Working as a requirement for Magnetism, ensuring that Frigates and Galleons cannot be built before Cannons.
Destroyers now require Electronics rather than Electricity, which ensures that they cannot be built until after industrialisation: before, it was possible to research electricity and build destroyers before ironclads become available. I have also added the AEGIS ability (double defence versus aircraft): they are still not powerful enough to survive being bombed, but at least they now have a chance to avoid being shot to pieces by Fighters.
AEGIS Cruisers can now attack loitering bombers.
I have changed the technology required for Offshore Platforms from Miniaturisation to Refining, as this seems more logical.
Conscription now requires Explosives rather than Gunpowder, keeping Musketeers in the field a little longer (as they now start later).
Riflemen are now made obsolete by Mechanised Infantry.
Horsemen now have double defence against other mounted units: however, they still have a basic defence rating of 1.
Crusaders have been removed, and Knights have been upgraded to give them an attack strength of 5, plus double defence against other mounted units (they are also more expensive, at 50 shields).
Cruise Missiles have been moved to the new Smart Weapons technology and made somewhat cheaper (40 shields rather than 60).
Fundamentalism has been replaced by Fascism (requiring Communism and Tactics). This government type is equivalent to Fundamentalism but with a reduced science penalty (30% rather than 50%) and the ability to spend up to 80% of income on science. Fascism only supports one free unit rather than ten, but certain unit types do not require support: the new Stormtroopers unit, plus Riflemen and any more primitive foot soldiers (Musketeers, Legions etc) that may still be in service. Fascism replaces Communism as the point where Marco Polo's Embassy expires and the United Nations can be built.
The number of freely-supported units under Communism has been boosted from three to ten, making this the best government type for supporting a large modern military force.
When Engineers use their Transform Terrain ability on Plains, the result is now Hills rather than Grasslands. Before, it took twice as long to make hills out of plains than out of grasslands (because of the need to make grassland first, then turn it into hills), and this has significant defensive implications (as fortresses are best sited on hills). The transformation of plains into grassland is still possible: plant a forest first, then transform the forest into grassland (which is closer to the way it is done in real life, where trees are planted to prevent soil erosion and improve water retention).
New Technologies
Advanced Horsemanship - this requires Horseback Riding and Warrior Code, and is a "dead-end" advance that can be skipped if it is not needed. It is most useful if you find yourself on a large continent, as it allows the Scout and Horse Bowmen units.
Quantum Theory - this is probably the most important scientific advance of the twentieth century, and I think it deserves a mention: without it there would be no solid-state electronics, lasers or superconductors. It requires Atomic Theory and Electronics, and leads to Miniaturisation (replacing Electronics), Lasers (replacing Nuclear Power) and Superconductor (replacing Lasers).
Jet Engine - this requires Advanced Flight and Mass Production, and allows the Interceptor unit. It also makes Fighters obsolete, and replaces Robotics as a requirement for Stealth.
Covert Operations - this requires Combined Arms and Guerrilla Warfare, and allows the Special Forces unit.
Smart Weapons - this requires Space Flight and Lasers, and allows Cruise Missiles and the Tactical Missile unit.
Advanced Tactics - this requires Smart Weapons and Combined Arms, and makes Alpine Troops and Paratroops obsolete, replacing them with the new Advanced Infantry unit.
New Units
Scout - this mounted unit has a movement rate of 3 and a vision range of 2 squares, allowing rapid exploration of large plains. They are made obsolete by Spies.
Horse Bowmen - these have the same combat abilities as Archers, but with a movement rate of 2, giving the best all-round combination of attack, defence and movement until Knights become available.
Longbowmen - these become available with Engineering, and combine the combat ratings of Archers with double defence against mounted units (as seen at the Battle of Agincourt).
Crossbowmen - these become available with Engineering. With an attack rating of 2 and a defence of 3, they provide the best all-round defence until Musketeers become available.
Siege Tower - this is also available with Engineering. It has an attack rating of 4, not as high as a catapult, but City Walls are no defence against it. It becomes increasingly ineffective as the quality of the defenders improves, and is finally made obsolete by Cannon (which cannot ignore City Walls, but which are far more powerful).
Stormtroopers - these replace Fanatics, and can only be built under a Fascist government. They have an attack rating of 7, a defence of 5 and a movement rate of 2, and cost 50 shields. They require no support under Fascism.
Zeppelin - this is the earliest air unit, available with Combustion. It is a weak bomber (attack strength 8) with a movement rate of 4, but with the ability to stay aloft for four turns, giving it the same range as a Bomber. It is made obsolete by Advanced Flight.
Interceptor - this is roughly midway between a Fighter and a Stealth Fighter in performance (Attack 6, defence 3, move 12), but offering double defence versus air attack, useful when scrambling to defend against incoming bombers.
Nuclear Submarine - all naval units gain a +1 speed bonus with Nuclear Power, but I do not think this is enough to account for the increased performance of nuclear submarines, hence this new unit (which makes conventional submarines obsolete). It has better combat ratings (attack 12, defence 3), is much faster (movement rate 5), and can detect other submarines.
Hovercraft - this is a light naval transport (3 holds) with a very high speed (8 points), making it ideal for racing through enemy-controlled waters to land spies or ground troops. However, it is not suitable for long voyages in the open ocean (like a trireme, it might sink). It requires Mass Production.
Special Forces - these have a wide range of special abilities which make them very useful against targets deep within enemy territory. They can make paradrops, can attack from a ship, move very quickly (movement rate 3, and they travel across country as if using a road), ignore enemy zones of control, and can infiltrate City Walls when attacking. They have the same attack strength as Marines, but their greatest weakness is their poor defence rating of 3 points: they rely on speed and surprise, and are not equipped for prolonged battles.
Tactical Missile Unit - this mobile missile launcher compares quite favourably with a tank in most respects: double the firepower, but slightly weaker in most other respects (attack 8, defence 4, HP 2, move 2). It has a two-square vision range, can shoot over City Walls, can attack aircraft in flight, provides double defence against aircraft, and provides double defence against Howitzers (plotting the trajectory of incoming fire and launching missiles at the origin). Be warned, however: Howitzers are still very powerful, and the Tactical Missile Unit will need luck and plenty of favourable modifiers to stop them (a mountaintop fortress would certainly help).
Advanced Infantry Unit - this represents modern general-purpose soldiers with the latest equipment, including shoulder-launched missiles and satellite communications. They can make paradrops, can move across country as if using a road (though not quickly: movement rate 1), and have a vision range of two squares and the best combat ratings of any non-mechanised unit (attack 10, defence 6), with double defence against aircraft.