For a long time Tan acted as the single passage "bridge" to the other northern color sims. It was also labeled as an "expensive" sim and was a popular location for some shops.
The Gassy Cat Workshop: The GCW was an early attempt by kohne Kato, Lance LeFay, and Christopher Omega to setup a scripting company. Its build was located in the very center of the sim, and when the project was abandoned, it remained as Christopher Omega's personal underground laboratory, script store and "open source cafe". Many, many, early discoveries took place here during beta and 1.0. This place was eventually sold to Jolene Jade by Christopher and the build was dismantled.
The Clock Tower: Apsinthion Protagonist built a beautiful clock tower in Tan during the early days of 1.0. It was so universally appreciated that when 1.2 came along with its new land-for-prims, people feared that its smallish plot could not support the necessary amount of prims, and a long discussion took place in the forums. People feared that the build would be deleted since its creator hadn't been seen online lately, and would thus be unable to delete surplus prims or acquire more land.
Tan Tower: The Tan Tower was built by Lordfly Digeridoo right after version 1.2 as an exercise in very large construction projects. It featured 15 floors, each one 20x20x20, and each floor was rented out to tenants.
It also had a working elevator. It was a bit of a minor landmark in SL, as at the time Tan was the only place that you could go through to get to the north continent (without teleporting, of course).