 Led Zeppelin 's next album , Houses of the Holy , was released in March 1973 . It featured further experimentation by the band , who expanded their use of synthesisers and mellotron orchestration . The predominantly orange album cover , designed by the London @-@ based design group Hipgnosis , depicts images of nude children climbing the Giant 's Causeway in Northern Ireland . Although the children are not shown from the front , the cover was controversial at the time of the album 's release . As with the band 's fourth album , neither their name nor the album title was printed on the sleeve . 
