Ultraman Tiga: S1 E26 - The Mysterical Monsterland Ultraman Tiga

On their way home from a drive, a family sees a strange rainbow and they pass under it. No matter how far they go, they can't reach the city and it would seem that they have somehow wandered into another dimension. It is a terrifying monster world where the Monster Gagi and Monster Silvergon are out on a rampage!