Visiting boneyards

[Regnum]

Have you ever visited a boneyard? Or catacombs?

A cemetery has a particular vibe. When you go there, it seems like time stops. When you pass the doors you leave the normal worlds and enter a place where everything seems solidified and quietly breaking down.
But if you go to a more intimate place for the dead, such as a boneyard or catacombs (perhaps this is the case with some crypts as well), things get different. A subterranean place where you get face to face with bones feels way more "haunted" than an open air area full of crosses.

Some years ago I had the opportunity to visit the unofficial Paris Catacombs in France. Part of the mine drifts have been used as a boneyard, especially under the Montparnasse cemetery (2nd wider one of the whole city).
When I went there, that is, from another place inside the underground network to the boneyard under the cemetery, I felt the air becoming colder. There were bones, skulls, neither voices nor ghosts, everything is very quiet but the very temperature is chilling. From a purely physical, non-magical point of view, this is not supposed to be: every other place underground is warmer.

Can the massive presence of bones in a drift, or the presence of a cemetery above, cause physical chilling?
From what I've read all this could carry some "psychical residue". Never perceived it though.
Have you ever explored this kind of place? If so, have you perceived something, performed a particular ceremony...?
Some say trying to invoke a particular entity in a cemetery is particularly dangerous due to the high number of entities and/or density of "psychical residue" there.

If you want an idea of what you can meet in a non-official boneyard, you can check a few photos there: http://parisboneyards.deviantart.com/gallery/