The Fountain of Youth

What would a Repository of Dangerous Things be without a Fountain of Youth? It isn't in Florida, it's in Boston. All the living things in this room use this water, which essentially grants them everlasting life- they do not age, wither, or die, unless they are picked or otherwise come to outside harm. Obviously, the Fountain isn't marked. 

The Fountain of Remorse

A separate source of water than the Fountain of Youth above - this decorative garden junk causes the drinker to re-open old wounds. Worst memories are re-lived, worst pains are re-experienced, and worst meals are re-tasted like a bad belch that won't go away. Most people who drink from the fountain wish they hadn't done so. Doesn't hurt the plants, though.

The Poison Patch

Most of the plants in the picture above are deadly on touch, ingestion, and sometimes through the air. Don't stray from the path, you'll die (unless you've drunk from the Fountain of Youth recently).

Ravel Tree

This leafless tree was on the premises when this section of the R.D.T. was built around it. An attempt was made to remove it, at which time the tree unwound itself with alacrity and thrashed the workmen to their helpless, mewling deaths. The curator at the time noted that a core of the tree near the roots remained tightly wound around something, but was unable to determine what. It is generally assumed it is guarding whatever it is holding inside it, for safekeeping. Or eventual mass destruction.

Troll Bridge

A poisonous, deadly garden is just the place for a structural throwback to the middle ages. The troll under this bridge is about the size of a cat, and he lives in the crumbled section. He casts a mean curse, however, and he demands payment of a strand of hair for each crossing. This gave Davis trouble during his bandana period.

Gila Rock

Gila monsters spend 99% of their lives underground, which is why you don't see it here. They are also one of only 2 venomous lizards in the world. Some idiot captured one from the wild and gave it to their young son as a pet. After it killed him, it escaped. Ms. Harper found it and gave it a home in the Courtyard. The entrance to its lair is behind and semi-under the rock.