Environment Book Series
The Environment series were a series of splatbooks for Dungeons & Dragons 3rd Edition that focused on different types of environment.
Frostburn
Frostburn focuses on taiga and tundra environments as well as supernaturally cold planes. On the crunch side, it adds a bunch of ice themed abilities.
Mechanically it is notorious for introducing the Shivering Touch spell, which does 3d6 (~10.5) points of dexterity damage that stacks with itself for a third level spell. This spell is absolutely bonkers since enemies rarely have that high a dexterity score, and even ones that do will rarely survive multiple hits from it.
Sandscape
Sandscape focuses on badlands, desert, and wastelands. Unlike Frostburn, there's not that much fire or extraplanar material. On the crunch side, the book adds a bunch of sand based stuff and heat themed abilities that focus on impeding and exhausting enemies instead of just making them burn. Refreshingly, Sandscape doesn't focus much on the pseudo-Egyptian pyramids that seem to dominate "desert" adventures.
Stormwrack
Stormwrack focuses on aquatic adventures, be they lake, sea, river, ocean or the plane of water. The part most people care about however is the ship-based stuff, with rules for alternate types of ships and naval combat.
Cityscape
Cityscape focuses on urban adventures. It includes how to distinguish cities from each other, locations within cities, who lives in cities, and how the surrounding area effects a city as well as what to do on an "adventure" in the city. On the mechanical end, there's intrigue focused spells and character options.
Dungeonscape
Dungeonscape focuses on subterranean adventures, including those in stereotypical dungeons. There is also advice to building better dungeons.