What Was "garum" and "liquidem"?

I’ve been reading some books about ancient Rome, and it seems that the Romans were great lovers of food. In particular, they liked to douse their foods with sauces-two of these were called “garum” and “liquidem”. According to my sources, they were made from some kind of fish (fermented, it seems!). Has any modern chef recreated these sauces? Anybody know what they taste like? Maybe the Roman Empire fell because of mass food poisoning?
Seroiusly, I would like to taste these 9if there is a modern equivilent).

Here ya go:

http://www.pbs.org/wgbh/nova/lostempires/roman/garum.html

Mmmm, I can almost tast the rancid fishy goodness!

Thai/Vietnamese-style fish sauces might be similar. Worcetershire sauce is somewhat similar as well, in terms of ingredients, although those recipes sound fishier.

Garum sounds somewhat like anchovy sauce, only slightly aged. I think the salt in the old recipe would keep it from going bad.