SYSTEM REFERENCE DOCUMENT 3.5
Above and beneath the Streets
Rooftops: Getting to a roof usually requires climbing a wall (see the Walls section — City Buildings, Walls and Gates), unless the character can reach a roof by jumping down from a higher window, balcony, or bridge. Flat roofs, common only in warm climates (accumulated snow can cause a flat roof to collapse), are easy to run across. Moving along the peak of a roof requires a DC 20 Balance check. Moving on an angled roof surface without changing altitude (moving parallel to the peak, in other words) requires a DC 15 Balance check. Moving up and down across the peak of a roof requires a DC 10 Balance check.
Eventually a character runs out of roof, requiring a long jump across to the next roof or down to the ground. The distance to the next closest roof is usually 1d3×5 feet horizontally, but the roof across the gap is equally likely to be 5 feet higher, 5 feet lower, or the same height. Use the guidelines in the Jump skill (a horizontal jump’s peak height is one-fourth of the horizontal distance) to determine whether a character can make a jump.
Sewers: To get into the sewers, most characters open a grate (a full-round action) and jump down 10 feet. Sewers are built exactly like dungeons, except that they’re much more likely to have floors that are slippery or covered with water. Sewers are also similar to dungeons in terms of creatures liable to be encountered therein. Some cities were built atop the ruins of older civilizations, so their sewers sometimes lead to treasures and dangers from a bygone age.