The Samara Bathtubs by Porcelanosa are outstanding.
Each tub is carved from a single block of Spanish marble. It takes at least 7-days to carve, shape and polish each tub.
The tubs weigh 1300+ pounds and each one takes 6 people over a week to fabricate it. This is after they mine it and transport it from a Spanish marble quarry.
The result is a beautiful tub with a smooth glossy surface finish that will cost you $38,000.