There are several good running routes around Gravesend – Pants has mentioned Shorne Country Park and Trosley – Camer Park and the surrounding woodland and fields is also a good place to run (beware of the dog walkers though) as is much of the farmland and woodland to the South and the East of the town.
The Saxon Shore Way heads East from Gravesend and follows the Thames crossing the Cliffe peninsula to the Medway – some excellent running although it get bleak in winter.
The Wealdway heads south from Gravesend crossing the North Downs Way and the Pilgrims Way – very many good routes around here.
Also some good routes around the surrounding villages – Higham, Shorne, Cobham, Sole Street, Nurstead, Meopham, Harvel, Vigo, Hodsoll Street, Fairseat, Stanstead, Ash, Longfield, Southfleet, Istead Rise, Ifield etc. Further afield there are places like Cliffe, Upnor, Wainscot, Cuxton, Halling, Snodland, Birling, Ryarsh, Addington, Wrotham, Borough Green, West Kingsdown, Hartley and the Darenth Valley (Kemsing, Otford, Shoreham, Eynsford etc). The North Downs offer some really good trail running (and some great views) and quiet country lanes.
Even further afield there is the river Medway – some good towpath running from Allington Lock all the way through to Tonbridge. Also on the Kent/Sussex border there is Bewl Water, the largest stretch of water in South east England – fabulous place to run (the Bewl 15 is a very popular annual race).
A personal favourite place to run in the summer months is the Isle of Sheppey and the nature reserve to the East of Harty Ferry - some good waymarked paths and bags of wild life.
Our club organises trail runs for all abilities every few months starting and finishing at a point on the outskirts of Gravesend – we run for around two to two and a half hours hours ending up at a café or tea kiosk at one of the country parks – you’re welcome to join us as are any other runners who may be interested.