Nicolock SERA TRAV 9" x 4" Serafina Split Face Wall Blocks Travertina have a versatile trapezoid shape that can easily be arranged in lines, curves and circles. Standing 4 inches tall with a double-sided split face, Serafina wall blocks are great for constructing freestanding and retaining walls that are shorter than 3 feet tall. Use them to build walkway barriers, outline gardens or create custom fire pits and planters.