Stephen Thomas Erlewine at AllMusic: Led Zeppelin returned from a nearly two-year hiatus in 1975 with the double-album Physical Graffiti, their most sprawling and ambitious work. Where Led Zeppelin IV and Houses of the Holy integrated influences on each song, the majority of the tracks on Physical Graffiti are individual stylistic workouts. The highlights are when Zeppelin incorporate influences and stretch out into new stylistic territory, most notably on the tense, Eastern-influenced "Kashmir." "Trampled Underfoot," with John Paul Jones' galloping keyboard, is their best funk-metal workout, while "Houses of the Holy" is their best attempt at pop, and "Down by the Seaside" is the closest they've come to country. Even the heavier blues -- the 11-minute "In My Time of Dying," the tightly wound "Custard Pie," and the monstrous epic "The Rover" -- are louder and more extended and textured than their previous work. Also, all of the heavy songs are on the first record, leaving the rest of the album to explore more adventurous territory, whether it's acoustic tracks or grandiose but quiet epics like the affecting "Ten Years Gone." The second half of Physical Graffiti feels like the group is cleaning the vaults out, issuing every little scrap of music they set to tape in the past few years. That means that the album is filled with songs that aren't quite filler, but don't quite match the peaks of the album, either. Still, even these songs have their merits -- "Sick Again" is the meanest, most decadent rocker they ever recorded, and the folky acoustic rock & roll of "Boogie with Stu" and "Black Country Woman" may be tossed off, but they have a relaxed, off-hand charm that Zeppelin never matched. It takes a while to sort out all of the music on the album, but Physical Graffiti captures the whole experience of Led Zeppelin at the top of their game better than any of their other albums.

Wiki: Physical Graffiti is the sixth studio album by the English rock band Led Zeppelin. It was released as a double album on 24 February 1975 by the group's new record label, Swan Song Records.

The band wrote and recorded eight new songs for the album in early 1974 at Headley Grange, a country house in Hampshire, which gave them ample time to improvise arrangements and experiment with recording. The total playing time covered just under three sides of an LP, so they decided to expand it into a double by including previously unreleased tracks from the sessions for the earlier albums Led Zeppelin III, Led Zeppelin IV and Houses of the Holy. The album covered a range of styles including hard rock, progressive rock, rock 'n' roll and folk. The album was then mixed over summer 1974 and planned for an end-of year release. It was delayed because of the sleeve, which was designed by Peter Corriston and featured a theme around a tenement block in Manhattan, New York City.

Physical Graffiti was commercially and critically successful upon its release and debuted at number one on album charts in the UK and number three in the US. It was promoted by a successful US tour and a five-night residency at Earl's Court, London, and has since been viewed as one of the group's strongest albums and the artistic peak of their career. The album has been reissued on CD several times, including an expansive 40th anniversary edition in 2015. Physical Graffiti was later certified 16x platinum in the United States by the Recording Industry Association of America (RIAA) in 2006, signifying shipments of over eight million copies. Full article