I'd start w/ lots of money, a site w/ adequate drainage, zoning, govt. approvals, etc., and a good design. If you have that, most everything else will take care of itself.

It would certainly pay to visit/drive other tracks of a similar scale to what you'd like to do, b/c there's no substitute for personal experience to figure out what works and what doesn't.

FIA approval is critical if you want to attract F1 (and, I assume, other FIA-sanctioned races) to hold a round at your track.

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'07 Guards Red Cayman S
'08 Honda Ridgeline RTL
'99 Miata 10th Anniversary Edition
'07 KTM Super Duke 990
'07 KTM 300 XC-W / '06 KTM 450 XC