Complex sentence: Kimura believes he can identify a pyramid, castles, roads, monuments and a stadium, and has surmised that the site may be a remnant of the mythical lost continent of Mu.
Split into simpler sentences: Kimura believes he can identify a pyramid, castles, roads, monuments and a stadium. Kimura has also surmised that the site may be a remnant of the mythical lost continent of Mu.