Columbus completed four voyages over 12 years, but he was lucky. Cabot, the 'discoverer' of continental America made one successful voyage. Despite having an able crew of his voyage of five vessels only one, which turned back, survived.

However in Civ you can pack a caravel full of settlers, set sail west (or east) and set up a toehold in the new world. It doesn't matter what the currents or winds say, you can go straight against them.

Also it is far too easy to found a colony. Many people think that once Columbus returned from the Caribbean people set off to found colonies. This is not true. In 1585 a group of colonists tried to settle in Virginia, and disappeared without trace. The first successful colony in the modern USA was founded in 1607. You do not land, found and conquor as soon as you find a continent.

However, there are huge disadvantages to that system. First of all, you can't really explore, and the game is based on exploration. Second, you can't find enemies that easily, and if you do, it would really suck to watch your army just disappear, and wonder why your enemy's does not.

One advantage of that system, however, is that it would allow more players on a certain map size. Since there is a penalty for exploration, empires will most likely remain quite small, centralized, and weak until the specific tech is reached. Thus, on a large map, you can have double the amount of players on the same size map.

As I suggested some time ago about movement on unfriendly type of terrain, use of routes etc., Firaxis developed in SMAC the use of "strenght points" to reproduce unit damages after combat.

We can suggest to extend this concept to loss and damage taken during exploration of unknown parts of the world.

If a unit is wandering around, it will take (e.g.) 5% of damage every turn it spent outside of known terrain. Sea units as trireme can take more damage, to reproduce the previus concept of risk loosing a trireme far from shores (shores will be considered "known" for this use).

To avoid cheat as a chain of units moving "one over the others shoulders" the check about "known terrain" must be done with previus turn status.

Explorer and fast units will have benefits, the former because more trained to explore, the latter because they move quicker in proper terrain (same damage taken by any turn, but exploring more).

If you use a fast unit on plain terrain you can go outside for a square (now marked as known), then go back to safe terrain. We must decide if it can be allowed, surely it make exploration a choice from more risky attivity or a slower one.

For me, any tactical decision a player must do is some spice added to this kind of game. Do you agree?

However, I think one turn is a little short. I think that the system should be either three turns or when two of your units have passed over the specific terrain. This will encourage units (such as explorers) to band together. Horsemen (and other units with two movement) will still be a problem.