I concur with Froggie, You can store alot of objects, so make use of that, outside objects use say 1-100, room 1 use 101-200, etc. and when your outside, delete the last building objects, and ait for the user to enter another building.
for instance: (not actually code)
` Scene 1 - Village
Load Villages Objects 1 to 100
` User walks around - blah de blah
` User Enters a 2 roomed building
Load Room 1 Objects 101 to 200
Load Room 2 objects 201 to 300
` User walks around a bit then leaves
Delete objects 101 to 300
` User spots a MAHOOSIVE mansion with 3 floors
` And 5 rooms on each floor
` User Enters
Either Load entire objects 101 to 1600
Or Load Floor 1 objects 101 to 600
-When User Moves up a floor Delete 101 to 600
-Load Floor 2 Objects 101 to 600
` User gets bored and enters village
Delete all objects 101 +
Rather strange way of getting my forts across but hey. it works it lamens terms