City of Glass

From Manuel of the Planes (3e):

For travelers with less of a taste for palace intrigue, the City of Glass is an ideal gathering spot on the Water Plane (especially for travelers who breathe air). Located at a stable collection of portals to other planes (stable in that they do not move in relationship to each other), the City of Glass consists of a great sphere of unbreakable glass, half-filled with water. Visitors enter the city through any number of openings along the water side, or through magical portals in the air-bubble half. Many buildings cross the boundary between air and water; there are buildings filled with water in the air half, and buildings equally stocked with air beneath the water’s surface. By mutual agreement of the city’s residents, “down” is toward the water half of the sphere.

The City of Glass is a cosmopolitan collection of traders, travelers, and expatriates from other planes. Its denizens are primarily from the aquatic races of the Material Plane, including merfolk, aquatic elves, kuo-toas, lizardfolk, locathahs, and sahuagin. It is ruled by a council of longtime residents, no two of whom may be of the same race.

The City of Glass is a merchant’s freeport and actively encourages trade. Mercanes may be found within its borders, along with marids, dao, and human traders. Several of its portals lead back to the Material Plane, and it is said that in secret places within the city, there are portals to other planes as well.

Historians note that the “unbreakable” glass of the dome has been broken in the past*. Without definite gravity, however, the air remained more or less where it was. The city officials immediately repaired the rift and put to death the visitors whose errant spells were responsible for the break.

The Heroes of the North also cracked the dome surrounding the City of Glass when they teleported to the Water Plane with the Blade of Fiery Might (see "We Chose this Life"). This crack worsened, eventually leading to the Heroes of Verdun embarking upon an epic, multi-planar quest to repair it (see "Let's Get Weird").  They gathered Elemental Sand from the Earth Plane (see "Let's Rock") and turned it to Elemental Glass by use of Elemental Lightning on the Air Plane (see "Join the Club").  Luethil Gilyth tempered the glass in the reignited Iron Forge, powered by a hearty Fire Elemental team.  It is unclear how this attempt to repair the dome played out (see "No Pressure").