Dover is usually seen as just the ferry terminal and a possible place for a night's stop-over. But even if for those living there, Dover has a distinctly down-market feel, to a tourist Dover has a lot to offer and it's certainly worth a weekend or a few day-trip visits.
THE TOWN AND SIGHTS
Dover goes back to the Romans: in fact you can see remains of Roman lighthouses in the castle and at Western Heights as well as some ruins of Roman foundations and a Roman painted house in town.
It was always the principal crossing point to France and it still remains so, having a claim to being the busiest ferry port in the world.
What is interesting about Dover is that it is NOT like the other coastal towns - it has nothing seasidy-resorty about it. It is shabbier, yes, it doesn't have the Regency or Victorian seaside promenade, no pier as such, no rock sold on the seaside; and it doesn't seem half as dead even in the middle of winter as a lot of the resort towns do.
It is also built along a deep valley and doesn't have much of a seafront. There is a bit with some beach and a promenade, but no usual seaside tat; just a pebbly beach and a square mile of sheltered waters for rowing or dinghy sailing in the part of the port between Eastern and Western docks. A walk along the Prince of Wales pier is worth taking for the views of the port, sea and cliffs; and there is a fairly mediocre cafe at the end by the lighthouse (a cup of tea is a cup of tea, however).
There are boat tours of the port in the summer (5 GBP/person) which are fun for those interested in shipping in particular.
The principal sight of Dover is its castle, dominating the town from its position on the top of the eastern cliffs. There had been a manned garrison here since the Norman times until the 50s and the whole site is a maze of buildings, walls, battlements, tunnels and towers well worth a half-day visit and the 8.50GBP entrance fee.
The main parts of the castle include the Roman lighthouse and the Saxon church of St Mary-in-the Castro (reputedly the best Saxon church in Kent), the medieval keep with its engaging exhibitions on travelling court of Henry the VIII, the wartime tunnels which are open to visitors and with multimedia displays allow a glimpse of the life in Dover fortress during Operation Dynamo (evacuation of Dunquerke) and the WW2 and medieval tunnels. The walk on the battlements is perhaps the most attractive part of the whole castle experience as it allows for breathtaking views of the surrounding countryside, port and town as well as Napoleonic-time fortifications on the Western Heights.
-Other Sights in Town-
Other sights include the museum - the interesting part is the Dover Bronze Boat gallery; showing remains of what was the oldest found seagoing boat in the world (3 500 years old) with a lot of background information in a high-tech gallery on the top floor of the Museum.
The exhibition with models of Dover port showing its development from modern times till now is also very interesting if you are into this kind of thing.
The Museum is attached to what is called Dover Discovery Centre and what houses amongst others a new library, UKonline centre with free Internet access (do not bother with the Internet cafe unless UKonline is closed and the library computers are occupied).
Crabble Corn Mill is apparently the oldest working mill in England, one of the many that were built along the banks of River Dour. There is a cafe, free educational exhibition in the basement and a a guided tour of the mill itself (charge applies).
The best sight of Dover is not really in Dover tough and it's the famous, famous White Cliffs. There are actually two of the cliff areas - one of them to the west towards Folkestone (Shakespeare Cliff) which looks absolutely spectacular as you drive into or out of town on the A20. To get there drive/take a bus to Aycliff and cross the A20 on foot or drive to Capel-le-Ferne and walk from there.
The eastern cliff area starts at Langdon Cliffs just above the Eastern Docks and is in my opinion definitely more interesting. Either drive to White Cliffs Visitors Centre (cafe and information at a kind of gateway to the cliffs run by National Trust) or take the bus/walk to Eastern Docks and then follow the footpath up to the cliff-top.
Less famous and perhaps unknown to anybody but the locals and specialists in military history is area of Western Heights; also a bit of a cliff hiding massive military fortifications from Napoleonic era - very impressive in a grim way but now a nature reserve protecting lost of valuable wildlife. There are three clearly sign-posted walking trials.
Very easy reachable by car (less than an hour from southern M25 in good traffic); Dover is surprisingly hard to get by public transport. Train from Waterloo East or Charing Cross takes about 2 hrs and costs 20 GBP for a day-return; a National Express coach takes over 3 hrs to Victoria at the cost of 11 GBP day return (the time makes day return not a terribly viable option).
If you are staying in Kent, there is plenty of local public transportation from the likes of Ashford, Canterbury and coastal towns.