i vote for a respiratory system. i want to travel all the way from the mouth to the lungs.

right outside of town pls.

Just out of curiosity, does this work? Have you ever tried it? Personally, I like to spring a new area as a "surprise" to mortals.

This could be a fun way to entertain players and let them know that the admins are indeed listening to what they request. However, it's probably a good idea to keep this kind of thing limited. Lots of players tend to only want things that are going to benefit them. They very well may start saying, "We want another EQ zone with uber-l33t EQ!".

Lot

I've done something similar to this before. I've asked people what they want and then assembled an area based on some of the ideas. Personally, I don't like to do it very often, because I have a hard time getting into an area that's been defined for me.

I have considered having the mortals suggest areas they want to see, and put them up on a page where builders can pick from them if they're having a hard time choosing an area idea. That way a builder doesn't get stuck with an area they don't want.

I recently completed an area that was geared towards one of the classes because throughout the rest of the game there was very little in the way of good equipment for this class. It was suggested by a player (yes I am quite sure he had a character of the class in question) but it was something that the immortals also had noted.  Several other players suggested to create areas (within the mud's theme) geared towards each of the 9 classes we have. It something I am considering doing.

The area I built does contain items that would be useful for all classes but its mainly geared toward one particular one. I think that we could possibly do areas  similar in nature for all the classes. Something that we have always done is take all suggestions from our players into consideration and we do let them know one way or the other about their suggestions. We found that this gives the players encouragement to present their ideas. If we don't use it, we explain why it was decided against rather than them thinking oh they just don't care.

Just my thoughts

You might also want to consider creating areas geared towards a specific combination of classes - for example, one which requires a thief (to open certain doors) and a mage (to cast "fly" on the party), or one which requires a cleric (to make a prayer at a specific location) and a warrior (to bash open a barred door). Of course this won't work for all muds, and you'd have to have some way to prevent people using potions/scrolls/etc - but muds are supposed to be about interaction with other players, and something which forces you to cooperate with other people will help emphasis that point. In general I'm not fond of classes, but one thing they really are good at is preventing self-sufficient characters.

On a similar note, we currently have an area being built that will require several races to complete (a troll, a human, a dwarf, etc.). I'm not sure how players will take to it but it's definitely an interesting twist.