Here are a number of preposition combinations that can be used to describe the floor plan:

Prepositions of Position

at the back of

at the bottom of

at the top of

behind

between

in the corner of

in the middle of

next to

to the left of

on the other side of

to the right of

on the side of

on top of

opposite

Example Sentences

There is a large garden in the middle of the skyscraper.

The smallest room is located to the left of the internal garden.

The entrance to room number three is opposite the entrance to room number two.

Here are a number of preposition that can be used to show direction and movement around the floor plan:

Prepositions of Direction

across

between

into

out of

past

round

through

towards

Example Sentences

Walk through the exit of room two and enter into building number three.

Walk across the indoor garden to reach room number five.

Walk past the side entrance to reach the main entrance.