So I'm not completely clear how to handle spaces with facedown remnant cards. When you land on the space, you turn up the card(s) and then choose whether you want to encounter that card or not? On the Ruins, you turn up both and you can choose one, both, or neither card?

Cataclysm Rules:

When a character lands on a space with a facedown Remnant
card, he flips it faceup before deciding to encounter the space
or a character on it. A faceup Remnant card counts as an
Adventure card for all abilities and effects.

So on the Ruins you turn both up then decide if you want to encounter the space or any characters on the space. Once you decide to encounter the space you must encounter all cards there (unless one stops your turn).

Well I understand the rules as written, but I'm not seeing many instances, except for at the very beginning of the game, when there would be both another character AND facedown remnant cards in the same space

Well I understand the rules as written, but I'm not seeing many instances, except for at the very beginning of the game, when there would be both another character AND facedown remnant cards in the same space

Unless you lose battle - psyc and are moved to the space (eg lost to eagle king and crags) or some spells like Transference:

I thought we were to encounter the Remnant Cards first, then the Space. I'm a little unclear on the Remnant Cards too.

It's basically a predeternined adventure card draw, when you land on a space with a facedown remnant you flip it over, and IF another character is present decide to encounter the space or the character as always. If there are no characters you encounter them as normal.