Dimrost was a cascading waterfall on the stream of Celebros, where it flowed down to meet the River Taeglin on the borders of Brethil. The falls raised a fine spray into the air, from which they took their name, which means "Rainy Stair". Above Dimrost, the Men of Brethil had constructed a wooden bridge to cross the Celebros.
From the bridge, a wide view could be seen, showing the Ravines of Taeglin two miles (3.2 kilometres) distant.
When Níniel was first brought to Brethil, when she saw that view from the bridge, she started shivering uncontrollably - so much so that the name of Dimrost was changed to Nen Girith, the "Shuddering Water". It was only later that the cause of her foresightful fear was discovered: the Ravines she had seen from the bridge would be the place of her tragic death.