A nice singletrack showing you the best bits of the Helsinki Central Park. The route is mostly signposted, apart from the northern loop. There are loads of trails criss-crossing, so you're better off with a good navigation device.
From the Main railway station, head north pass the Olympic Stadium (leave on your left) and on to the Aurora Bridge. After the bridge, turn left and you're at the north end of Laakso Equestrian Field. This the trailhead.