Preposition of Place: In and On

They have lots of pictures (a)   their fridge.

We put the old books (a)   a box.

Last summer we stayed in a cabin (a)   a lake.

My office is (a)   the 20th floor, so I take the lift.

There are important Roman ruins (a)   Jordan.

Their house is (a)   the James River.

Buckingham Palace is (a)   London.

Her flat is (a)   the sixth floor.

Please put the flowers (a)   the table.

I'll meet you (a)   the bus stop.