After spending two years in a nursery near Marathon, over 600 large olive trees which were removed during construction work at the Markopoulo riding center have been successfully replanted at other Olympic venues, Games organizers said yesterday. The Athens 2004 organizing committee said the 656 trees ranged in age from «several decades to centuries old» and have mostly been re-installed near their original positions. The whole operation cost 175,000 euros, which, according to Athens 2004 Environmental Director Giorgos Kazandzopoulos, was quite a bargain. «The entire effort cost about one third of the funds we would have needed to buy such trees on the market,» he said. Apart from the 381 olive trees restored to the riding center, 155 have been planted in the Faliron area, 100 at Hellenikon and 20 at Schinias.