Carr Properties announced March 31 it has partnered with Austin-based Manifold Development to develop an office tower of up to 738,000 square feet on what’s known in real estate circles at Block 16, at Trinity and Second streets. That would make it the largest pure office building in Austin. Meanwhile, plans are coalescing for what could be the tallest tower in Austin just to the south, at 98 Red River St. Click through for more details and to access ABJ’s list of the biggest office towers in town.