By Tobias Carroll Whether they’re 100 years old or 1,000, historic buildings are something to savor — a tangible, tactile link to the past. But oftentimes, it isn’t enough to simply declare a building historic and move on. The upkeep of certain sites poses a host of challenges — and that’s before you get into the questions that can come up when sustainability enters the picture. Unfortunately, not all historic buildings have dedicated resources allocated to keeping them functional and accessible. And thus, you might end up with a situation similar to what’s taking place right now in Spain. A n…