Traditional Russian Fireplace labyrinthine brickwork, one of the earliest forms of masonry stove. They are substantially more efficient than open fires, but with limited air regulation waste a lot of heat up the flue when the fire is out.
"This is a masonry heater. The firebox and air chambers are constructed to promote a super hot-burning fire. The result is twofold: One fire a day will warm a 1000 SF conventional home, or up to 2000 SF of a super insulated strawbale home.