It was counterintuitive to me that by just building a road I got access to horses?
Yes, that is how the Strategic- (and Luxury-)resource model works in Civ III.
To be able to build the units and buildings which require them, your towns must be connected to Strategic-resources via your "trade-network":
— By roads (if the resource is inside your borders)
— From Colonies, with a road to your territory (if the resource is still in unclaimed territory on your landmass)
— Via Harbours if (the resource is on a different island, and) you have all the tech(s) required to trade across all the intervening water-tiles; note that you can also use Harbours in towns controlled by friendly AI-Civs
But you can only
trade resources with other Civs, if those resources have an uninterrupted trade-network connection to your Capital
I'm not sure if it was the case but I thought I had to build a pasture.
If you are playing the default Conquests game, there is no such building as a "Pasture"*. If you are playing a mod, you would need to specify which one.
*Unless you mean that the Worker should also
irrigate the tile...?
It was interesting not see rivers on continents 70% water map.
The water-percentage refers to the (approximate) proportion of the map taken up by Coast, Sea and Ocean tiles, i.e. "70% water" = "30% land".
I am not sure if it is possible to increase the number of rivers generated on a Random map. The "Humidity" setting (Dry/Normal/Wet) at the setup screen affects how well
vegetated the map will be (i.e. number of Forest + Jungle-tiles; possibly also Marsh-tiles), but I do not know whether that setting also affects the number of rivers.
Lastly, how does someone know if the mod its installed, is there any sort of indication once the game starts?
Again, that depends on which mod you are talking about?
Nearly all Civ III mods consist of a ruleset (.biq) file, plus any required additional folders containing any added units, artwork, text and/or music. However, these are (usually) run using the same executable as used for the base-game, and the save-files for mods do not look significantly different to the unmodded game versions, i.e. their default filenames will still be of the form "
[Leader-name] of the [Civilization], [Game-date].sav".
Mod-files (.biq and other files) would usually be saved in the
../CivIII/Conquests/Scenarios folder. Mods stored here are accessed through the "Civ-Content" option on the first menu-screen.
Some modmakers ask that their mod be installed in the
../CivIII/Conquests/Conquests folder instead; such mods (e.g. "The Ancient Mediterranean" — or "TAM" for short) are then accessed using the "Conquests!" option on the menu screen (on a standard installation, this folder/option usually only gives access to the single-player historical "Conquest" mods prepared by Firaxis).
To the best of my knowledge, only the latest version of
@Civinator's massive "CCM" (and "RARR") epic-game mod(s) is designed to be installed in/ over-write the base-game files in the
../CivIII/Conquests/ folder. If CCM has been installed as instructed, then this mod will start when you select "New Game".
That said, CFC-user
@Flintlock has also recently been developing bug-fixing and GUI-improvement patches for the Firaxis game-executable. If you have installed his patches as instructed, his modded executable will be used to run the base-game (or any mod) instead of the unpatched executable from Firaxis. You will be able to see if this patch is running due to the slight changes to the interface (e.g. right-clicking on a terrain-tile will tell you whether it has already been "Chopped" for the Forest-shield bonus).