Penny Floor - don't know if I would have the patience for a whole floor. but a coffee or patio table would be nice! Also an easier way to do it is to put out the pennies then flatten then by, I don't know, maybe a broom or some thing.
Look at the Christ Pantocrator icon carved into the salt rock. Church in Underground Salt Mine in Romania. Several hundred meters below ground, it was built for the workers of the salt mine and has been seen by very few people in the world.