What more can be said that hasn't already been said better elsewhere, not least on the Eden Project's own excellent web site?
I can only think of two things:
- Crowded in Cornish terms is nothing like crowded as it is understood in other parts of the UK. We went at the height of the high season and it was no more than comfortably busy. Perhaps we were just lucky.
- When we were there (2003) on the first floor of The Link was a desk where you could book guided tours. They were not all that well advertised, and we ended up having a personally guided tour of the Warm Temperate Biome. The group for the Hot Tropics was a bit larger, but having a guide point to out things like a weird bright orange coconut that we would otherwise have missed, was well worth while.
Either way try to get to speak to some of the inhabitants; its one of those places with a philosophy that can profoundly touch you, if you let it. Here, the way they combine idealism and pragmatism is inspiring. Although I'm not totally convinced by the 'green' Coke machines.