There are many features of these palaces which are worth minute study. In the building of the great palaces it was the practice to prepare the ground with a thick mixture of lime and clay and pebbles. This mixture set so hard that it has now to be broken up with explosives before objects below can be removed. The staircase at Knossos measures nearly fifteen yards from side to side, and the steps are two and a half feet wide and hardly five inches deep. The most famous steps in Rome were not more than five and a half yards from side to side. The doors of the palace, of which there were many, were made to fit into the walls when open, so as not to interfere with corridor space. At Hagia Triada the drains of 4,000 years ago may still be seen working in wet weather. At Knossos the main drain, which had its sides coated with cement, was more than three feet high and nearly two feet broad, large enough for a man to move along it; and the smaller stone shafts that discharged into it are still in position. The water supply entered the palace from the north. In 1904 Sir Arthur Evans discovered some pipes in position to the north-west of the palace, running alongside the paved road which leads to the Theatral Area and the Little Palace. The necks of these pipes point eastward towards the palace and they lead from the very hills on the west from which the Venetian and Turkish aqueduct still supplies Candia. They must, therefore, have been aqueducts and not drains, and probably form part of the same system as the terra-cotta pipes discovered in the earlier excavations further east, and at the time considered to be connexions in the drainage system. They are thus described by Dr. Burrows: “Each of them was about two and a half feet long, with a diameter that was about six inches at the broad end, and narrowed to less than four inches at the mouth, where it fitted into the broad end of the next pipe. Jamming was carefully prevented by a stop-ridge, that ran round the outside of each narrow end a few inches from the mouth, while the inside of the butt, or broader end, was provided with a raised collar that enabled it to bear the pressure of the next pipe’s stop-ridge, and gave an extra hold for the cement that bound the two pipes together” (_Ibid._, p. 9).