This was our 2nd trip up Big Si, but our 1st up the Old Trail. 5 times harder than the main trail. Started out at Little Si Trailhead, and took the immediate fork onto Boulder Trail. We've done this loop before (twice) and love the peace & quiet of no other hikers. Amazing rock formations make for some great exploring here ! Near the top of Boulder, take the unmarked stone stairs up... this is the start of the Old Trail. It's a lot steeper than the new trail, and you'll feel it right away. It soon turns into a boot trail, and gets even steeper. If you've done Big Si before... this entire trail feels like the LAST 1/2 mile of the new trail. Get ready for an ass-kicking :0)