Of course, the one thing everyone sees in their minds when Easter Island is mentioned are the moai. Or the statues with the big heads, as they are often referred to. They have inspired many myths and there are still many archaeological controversies surrounding them.
So, there are many relics spread throughout the island, officially they are under the protection of the National Park, but there are so many of them that very often what you will see is a moai lying on the ground and surrounded by a small fence. What you can find in the highest numbers are the "ahu" - the platforms, around 300 of them across the island. Ahu have been part of every family/clan. They were mainly used as a burial place. Many of these platforms had standing moai. In close proximity to the platforms you can still see the stone foundations of the houses. They looked like boats upside down. Next to the houses you can find a henhouse - it normally belonged to few houses - also made of stone. Further away little stone circles, sort of little gardens. It's quite difficult for plants to release the roots in volcanic ground, the winds are also very strong and it hardly ever rains, so the circles protected the plants from the elements and kept moisture.
The moai standing on the platforms where always looking at the village so standing with their backs to the sea. The tallest one that is standing upright has 10 meters. It is a mystery why the Rapa Nui stopped carving them. In Rano Raraku, the quarry, it looks like they just left one day in the middle of work. Some tools were still lying around. They never came back to finish any of the statues they began to work on. Supposedly at the same time all standing moai have been knocked down. Nobody knows why, but all these places have been destroyed, probably by the clans themselves. According to some archaeologists and carbon dating, the last time someone worked at the quarry was in 1680. (Shocking precision!) Rapa Nui themselves are very sceptical about facts like that because every now and then some archaeologists come and announce that their theory is stone clad. What we know is that when first outsiders came to the island the Moai were still standing. After that with every visit more and more of them were found toppled down.
When the islanders talk about the history and culture they use phrases like "according to legends" or "as per some theories" etc. So according to legends passed down for generations the moai "walked" to the ahu themselves. And indeed, the island is full of moai that looked like they have fallen down while walking towards the sea. Once on the ground they couldn't get up, and they often broke. As the statues were sacred and the fall meant death the Rapa Nui had to go back and start carving a new one. The most logical mode of transport for the moai seemed be on wooden logs however erecting them later on would be quite difficult and there were no traces found on the moai themselves to support that. One of the latest and tested theories is that they were "walked" by rocking them on ropes by 3 teams of people. This one sounds most plausible and would explain the legends as well. You can even watch the re-enactment on YouTube.
As said before each clan had an ahu and on most of them today we find traces of moai. Theory is that they represented the spirit of the ancestors and watched over the village - hence they were looking at it.
According to archaeologists the ahu without moai are the oldest one. Then time came for the ones with statues. After that ahu got an additional step and the moai. The last ones were moai standing on the elevated platforms wearing a sort of a hat - pukao. Recently it has also been discovered that they had additional ornaments, their eyes were made of corals. But as they were pushed on their bellies, the coral got smashed into pieces. In the front the moai had carved out hands with elongated fingers - probably representing nails - and a navel. On their backs they had meke meke symbols - for sun and moon for example. The pukao might actually represent a Rapa Nui hair style, however we cannot be sure. It is also unclear how they were placed on the heads, as they were found on the ground and not attached to the statues.
The biggest danger for the statues are wind, moisture and ignorant tourists. Partially guilty of destroying the petroglyphs were the sheep brought from Australia - they just walked over the moai slowly speeding up the erosion. The restoration is also tricky. When people try to remove the deposited algae and fungi they damage the stone as the coating can go very deep. Some restorations brought ridiculous results. The heads were attached back to the statues with cement that can be clearly seen even from further away - they look like someone slit their throats.
Based on the findings in Rano Raraku, preparing one moai would have probably taken around 6 months. First, they would cut a huge monolith out of the rock already shaped to resemble the statues, then they would push it down into a pre-dug whole and start working on details. When they left the quarry, they have left a lot of the moai in different stages of work. With times the wholes filled up with soil and so the story of "big heads" started spreading around. The archaeologists who first started digging around the statues were quite surprised that the busts and heads randomly thrown around the hillside of the volcano turned out to be full sized moai. It is one of those "buried" statues that is 14 meters tall, but all you can see is the top sticking out of the ground - after the digs archaeologists had to put everything back the way it was, that included burying the moai back. The tallest moai, or rather the one with the potential of being the tallest in the world, was left unfinished. The block hasn't been completely cut out of the bedrock, it has 20 meters and is still lying down, however you can see the characteristic shape of the moai.
There are also two controversial moai and one controversial ahu, one of the statues is actually kneeling and the ornaments look very different, it is still in the quarry. The other one is clearly female - you can see the shape of breasts and the navel is different to the others. It is lying on the side of one of the roads. The third controversy is a group of seven statues on an ahu in the middle of the island. Not only is the platform not on the coast but those are the only moai looking towards the ocean. As per legend those are the seven sons of a Polynesian king who sent them towards the rising sun with a mission of finding an island that is like a navel, far away from everything else. They found the island indeed and the seven princes look into the seas waiting for the king to arrive.
As mentioned above the original inhabitants of the Easter Island actually come, like the inhabitants of Hawaii, from Polynesia. The only link apart from genetics is that one kneeling Moai that has symbols resembling the ones in Polynesia. All ahu and moai are on the UNESCO World Heritage Site list and officially protected by the National Park, however there is logistically no way of having a guard next to all of them. It is completely forbidden to step on the ahu and I must say, the tourists I have seen have respected the rules, even though there are no fences around many of the sites.
So which ones are the ones to see? One of the best-preserved villages is Ahu Akahanga, without moai. The most impressive platform with moai is Ahu Tongariki with 15 quite well restored statues. The best-preserved monoliths are at the Anakena beach called Ahu Nau Nau where the fallen statues were covered by sand dunes so there is almost no sign of erosion and you can admire the detailed carvings on them. The seven sons are called Ahu Akivi. If you're just walking around town you will find the Ahu Tahai, loads of tourist and the cement traces are clearly visible. Little bit further you will find Ahu Akapu with less tourist and a perfect spot for sunset.