Interchangeable integrated circuit building blocks include functionally equivalent integrated circuit building blocks, having similar footprints, and having one or more dissimilar features or operational characteristics. The functionally equivalent integrated circuit building blocks are interchangeable in a design layout without having to re-place and re-route. The functionally equivalent integrated circuit building blocks are optionally interchangeable on a building block by building block basis. One or more detection features are optionally included in one or more of the interchangeable integrated circuit building blocks. The detection features facilitate detection of the interchangeable integrated circuit building blocks. Area, space, and/or width design rule checks are optionally focused at junctions of detected integrated circuit building blocks.