My latest implementation used a free fall downwards (140 levels) and an impulse ramp based spiral track upwards. This was "secured" with track activated pressure plates controlling 4 doors (the beginning and the end of the tracks) to block cats, dwarves, and diplomats from becoming roadkill. If you don't want to use impulse ramps, I'd recommend a free fall pushed track downwards and a guided track upwards, as Larix said.
The way I constructed it used a 3*3 footprint with a vertial shaft in the middle, and a spiral around that. The spiral consisted of alternating impulse ramps and ordinary turning ramps, with the impulse ramps at the middle of the 3 tile strech and the turning ramps at the corners.
The construction was made in a two step process, where the first one was digging of channels (the description is from the bottom upwards):
z z-1 z-2 z-3 z-4 ...
SSS SSh hhS SSS SSS
ShS Shh ShS hhS ShS
Shh SSS SSS hSS Shh
S=Stone, i.e. solid rock, h=cHannel.
The second step was to carve all the ramps, where I set the impulse ramp to be the complete opposite of the natural turning ramp:
z impulse ramp: SE, corner ramp: NW
z-1: NE, SW
z-2: NW, SE
z-3: SW, NE
z-4: SE, NW again.
At the bottom the falling track ends in a straight ramp (i.e.NS or EW, depending on which direction you want the exit track to take). You probably need impulse ramps to power the to/from tracks at both the top and the bottom as well.
The top of the fall actually turned out to be trickier than I thought, since I ended up with the cart missing the shaft and instead hitting the spiral track and returning back up. I solved that by changing the falling shaft to start higher up than the spiral, so the cart would hit a solid wall on the other side of the shaft.