Rabbit hole

A Rabbit Hole is a building in The Sims 3 where Sims can visit.

It can provide either a moodlet or an item for their inventory, or be a workplace for the Sim.

You can not see Sims while they are inside a Rabbit Hole. as every place in The Sims 3 can be visited, all the places that aren't a house (neighbors) or have a roof on it (the Park and the swimming pool) are Rabbit Holes (except the Art Gallery).