Very complicated engines

I watched a video of a man disassembling a Porche 6-cylinder water-cooled boxer engine after it was damaged during a race. I could never believe it that the engine is very complicated. The engine had double camshafts with timing chain system similar to that on Ford V8 engines with DOHC. Splitting the crankcase reveled a cage holding the crankshaft, conrods, and pistons. How is the engine assembled?