I need help remembering a TV SHOW...it use to come on in the late 90s?

You might be too young to know but do you remember this show that use to come on…it was a family that was going on vacation and they fell inside the earth…and lived INSIDE the earth…they were the only humans inside…but it had water plant and animal life…they feel through a crack in the earth…I cant remember if it was an earth quake or something…but the name of it was like lost world or something…