Mountains of the Sun
Legend has it that the surface of the sun is a rocky mountainous region with lakes of lava and constant explosions of sulfurous gas, not unlike the elemental realm of fire. In fact, legend further has it that the sun is a direct portal to the realm of Fire.
Geography
The sun is mostly mountainous, and Thantros' manor house rests in some of the highest peaks. There are a number of large lakes of lava, but the entirety of the face of the sun is only a few hundred miles across, shaped like the inside of a bowl. There have been few travellers to the sun, and those that have could be considered unreliable at best, but scholars believe that the sun does in fact rotate around the world, and it is unknown who sees it when Selestyans don't.
Climate
Well, it's hot, and, yes, it is at least a dry heat. Sulfurous, smoky mountains, and lakes of molton lava, pretty much what you'd expect by the name. There's no climate or weather to speak of, at least in terms of variation, apart from windy days, which are due to the gusty explosions of fire, not actual air. So they don't really bring any relief.
Fauna & Flora
The sun is sparsely populated, primarily by the salamanders and phantom stalkers known to be native to the realm of Fire. There are supposedly a few efreeti as well, having been banished from the City of Brass. The phoenix is the only bird species known to inhabit the sun, but there are a surprisingly large number of trees (varieties of fruits native to Fire) and bushes (fireweed primarily) seen nowhere else (apart from the realm of Fire).
Type: Gate
Owner/Ruler