North of the Parthenon is one of the loveliest of all ancient monuments, the delicate Erechtheion, thought to have been built on the very spot where Athena and Poseidon had their contest for possession of Athens. Indeed, some said that the marks of Poseidon's trident are clearly visible in the rock; and, it is traditional for an olive tree to grow near the Erechtheion. The myth of the Erechtheion goes, that the Erechtheion was also the place where the goddess Athena allowed the sacred Olive tree to grow. The tree was destroyed during the Persian invasions, after which it miraculously began to sprout again. Alas, visitors today will see the exquisite temple through a screen of scaffolding. Like many of the monuments on the Acropolis, the Erechtheion is feeling the effects of time and urban pollution, and its elegant columns the Caryatid Maidens, have had to be removed and replaced with copies for preservation.