[russell]

From your second link: >>>The junction provides access to and from the A38 (Tyburn Road), A38(M) (Aston Expressway), the A5127 (Lichfield Road/Gravelly Hill), and several unclassified local roads. It covers 30 acres (12 ha), serves 18 routes and includes 4 km (2.5 mi) of slip roads, but only 1 km (0.6 mi) of the M6 itself. Across 5 different levels, it has 559 concrete columns, reaching up to 24.4 m (80 ft). The engineers had to elevate 21.7 km (13.5 mi) of motorway to accommodate two railway lines, three canals, and two rivers.

Truly an inspiration to those of us who grew up with Erector Sets and Tinker Toys.