For years, tourists to the Acropolis have been frustrated to find ancient monuments shrouded in scaffolding, thanks to a long and painstaking restoration project. Now, an end is in sight.

Greek cultural officials said Wednesday that work on the Parthenon, the Athena Nike temple and the massive Propylaea gate - treasures built in the mid-fifth century B.C. at the height of Athenian glory - should be finished by the end of next year.

``These three works will be finished at the end of 2006,'' said architect Haralambos Bouras, a senior project official. ``All three were vitally necessary, and failure to carry them out could have resulted in severe damage to the monuments.''

Still, more scaffolding could go up at the Parthenon - the biggest crowd-puller - as projects on the Acropolis hill are expected to continue until 2020.

The multimillion-dollar restoration started 30 years ago, but the complexity of the work and funding snags caused considerable delays, with scaffolding embarrassing authorities during the 2004 Athens Olympics.

So far, the ancient marble structures have survived wars, fires and earthquakes, not to mention decades of modern pollution. Botched restoration efforts in the 1930s used iron clamps that rusted over the years, causing the marble to crack and break.

Work on the Athena Nike temple, an elegant Ionic structure at the entrance to the citadel, started in 1998. The whole building had to be taken down to its foundations.

According to Maria Ioannidou, who is supervising work on all three buildings, the ongoing effort is ``the biggest restoration project currently under way in the world.'' The total estimated price tag is $84.4 million.

So far, nearly 1,000 blocks of stone have been removed from the three monuments and 1,100 parts have been assembled from ancient fragments. Restorers used marble from Mount Pendeli, north of Athens, whose ancient quarries provided the original building material. More than half of the blocks have now been treated and put back.

``We treat each piece like an individual work of art,'' Bouras said.

Only one of the four major Acropolis monuments, the Erechtheion temple, has been fully restored. In addition to the Parthenon, further repairs are needed to Propylaea and the wall surrounding the citadel.

Afterward, the hilltop will be landscaped with hundreds of tons of earth.