The Blackstone Well

During the construction of Blackstone Castle in the Briary of Molrick, a well was being dug to give the fortress a dedicated and safe supply of water in case of siege. At a depth of nearly 70', Blackbeard Dwarves found a truly ancient tunnel running directly under the castle's foundations. The tunnel runs basically north and south, and is easily 5,000 years old. The discovery of the tunnel came as a complete surprise, as no ruins such as these were ever suspected to be found within 200 miles of Molrick.
The tunnel is exactly 44' wide and 55' tall at its interior peak. The well shaft that initially accessed the tunnel happened to open up at the exact peak of the tunnel ceiling. The tunnel has about a foot of clear, clean running water flowing to the north along the tunnel's granite floor. The walls and ceiling are built of perfectly finished granite blocks faced with a patterned mosaic tile of various hues of colored granite, soft yellows, dark reds, rose and near-black hues of the speckled stone.
From the entrance shaft, the tunnel runs for about a half mile north (downstream) and south (upstream).  Both directions lead to evidence of catastrophic collapse with only enough gaps in the rubble to allow water to flow through.  About 100 yards from the northern terminus another shaft has been dug, in secret, that allows access to a stone warehouse in the town of Molrick itself.  Thus, one can travel safely and secretly from the interior of Blackstone Castle to the heart of Molrick, if the need should arise.

Purpose / Function

The reason for the construction of the tunnel is unknown.  If it were simply an aqueduct, it is certainly overly ornate in its decoration.  If it were intended to be an underground canal or viaduct, it is very, very shallow.

Entries

The tunnel is accessed through a pair of shafts dug during the construction of Blackstone Castle. Each shaft is 10' square and nearly 70' deep. Ascent and descent is either by ladders built into the shafts walls or by a derrick and lift that can carry up to eight men up or down the shafts.  The first shaft is located within the inner bailey of Blackstone Castle itself, and the other is in a large stone warehouse located in the town of Molrick nearly half a mile from the castle.
 All other exits from the tunnel are either hidden or blocked by collapse rubble.

Sensory & Appearance

The tunnel is cool, slightly damp and unless lit by lanterns or torches, utterly dark.  The water flowing along the floor is cold and clear and as fresh as from a spring.  The only sound is of the flowing water and the occasional drip from the high ceiling.

Special Properties

The tunnel is open for nearly a mile, with the entrance shaft roughly in the middle.  To the north (downstream) it ends at a natural collapse that has closed the tunnel nearly completely.  Only several gaps at the very lowest levels allow the flowing water to continue on its course.  To the south (upstream) is another collapse, but the expert Dwarven masons of Molrick have determined that it is a construct built to look like a collapse and not, in fact, natural at all.  Best estimates put the closer's construction date to roughly 2,000 years ago, but no where near as long ago as the initial tunnel construction.
No one knows why the tunnel was blocked in this manner, or who blocked it.

The Well under the entrance shaft at Blackstone.

RUINED STRUCTURE
Unknown

Founding Date

Nearly 6,000 years ago

Type

Ruins

Parent Location

Blackstone Castle

Owner

Crole Blackbeard

Owning Organization

Briary of Molrick