The next morning we arrived at the site and immediately entered the Jaguar Tunnel in the East Court.  You have to buy an additional ticket to enter the Jaguar Tunnel.  And this tunnel is very popular, so we visited it 1st before experiencing the rest of the site.  The tunnel contains some carved stone masks and heads.  The tunnel is worth checking out once for the novelty of it.

According to the LONELY PLANET GUIDE to HONDURAS, 1st Edition, January 2007, ISBN 978-1-74059-150-8, page 152, the Jaguar Tunnel is 700 meters (2,275 feet) in length, but only 80 meters (260 feet) running along the foundation of Temple XXII is open to the public.