Lay-out of the building.
The Erechteum was completed in 406 BC. It has a prostasis on the east side, a monumental propylon on the north and the famous porch of the Caryatids on the south. The main temple was divided into two sections, dedicated to the worship of the two principal gods of Attica, Athena and Poseidon Erechteus. A relief frieze, bearing the representation possibly of the birth of Erechteus, decorated the exterior of the building.
The west side of building, with its own monumental entrance, held the altars of Poseidon Erechteus, Hephaistos and the hero Butes. In this part were also the holes in the rock visible which were made by the trident of Poseidon during his disagreement with Athena, and the Erechteis sea which was the well of Poseidon which contained salt water and sounded like the wide sea when the wind came from the south. The hall of the caryatids was situated above the grave of Cecrops, the first king of Athens.
The cella of Pallas Athena was located in the east part. Here the old Archaic statue of the goddess was placed and lighted day and night by a very ingenius lamp which was invented by Callimachus who is traditionally credited for the invention of the Corinthic capitel. Above the lamp, which was only filled once a year, hung a bronze palmbranch which was supposed to remove the smoke from the temple. Furthermore old pieces of art were kept in the cella like the ancient wooden statue of Hermes, the xoanon, which was blessed by Cecrops, a folding-chair made by the father of arts Daedalus, and several trophies from the Persian wars as the suit of armour of Masistius and the sword of Mardonius, both Persian generals during the battle of Plataea.
The altars of Zeus Hypatos, of Poseidon and Erechtheus, of Hephaistos, of the hero Boutes, of the Thyechoos, and the very ancient xoanon of Hermes, all had to be accommodated harmoniously. Lastly room would have to be found for the sacred olive and the sanctuary of Pandrosos which included the altar of Zeus Herkeios. The architect succeeded by subtle and ingenious use of the differences in level to produce an astonishing temple which satisfied the requirements of all these cults. He respected the traditions and at the same time introduced striking innovations.
The resulting building may appear complicated at first sight, but it bears the mark of true genius and contains more original feature than any other structure in the Greek world. It consists of three almost independent sections (the main temple, the north extension and the porch of the caryatids) with three separate roofs, and is built at four different levels. Ionic columns of three different dimensions and proportions are used, and, following an old Ionian custom, use is also made of corai as supports for the entablature - the famous caryatids. The Erechteum is the finest expression of the Ionic order, yet the building loses none of the compact austerity of classical Attic architecture. The frieze of Eleusinian stone is of a deep grey colour, and relief figures were attached to it and secured by means of metal connecting pins set in the slabs.
More pictures of the Erechteum can be found below: