I am planning a tour of the Netherlands (I am leaving in 3 days) and I wanted to ask to the Forum Members (especially to Els and the other Dutch Members) if they have personal experience of these Tentative List sites:
- Alblasserwaard - Oost
- Bunnik - Vechten / De Burg
- De Gouw and de Groetpolder
- Swifterbant - Visvijverweg / Noordertocht
- Voorburg - Park Arentsburg / Forum Hadriani
Are there just archeological features hidden underground or invisible for a common traveller or is there something that one can see?

I don't have first hand experience of the sites, but having done a bit of looking into them it seems that they may not yield too many great delights.

The one that I found most on was Forum Hadriani
"Today, a beautiful model of the ancient town can be admired in the small but nice Museum Swaensteyn in Voorburg. One of the houses of Forum Hadriani has been reconstructed at the Archeon archaeological park at Alphen aan den Rijn. The remains of the ancient town are one of the monuments on the UNESCO list of world heritage.[sic] They are not visible; the modern park Arentsburg, near the Mariannelaan, occupies the site."

It is only in Dutch I'm afraid but this site has some up to date pictures of the dig at the site.

A Google Image search reveals four reconstructed posts in what looks like a car park!

From the list of sites that you put in your post this is the most substantial remains I have come across so far

Hopefully those with local knowledge can shed some more light on them.

To give a perspective of someone who has visited the Netherlands and focused on their WHS, don't make these sites the sole basis of your trip. If you do you will miss big chunks of the country that may actually be of some interest to you.

If I were being brutal I would only recommend a visit to the Rietveld Schroderhuis (you will need to book in advance, if you haven't already) and Kinderdijk as this is a good stereotypical Dutch scene.

The four other sites associated with Water management can easily be seen in a one-day round-trip in a hire car from Amsterdam. A fair few of the sites on the tentative list can be added to the list as they are on the route, but on the whole these are not must see sights.
The only real plus point I could say on visiting these sites was that you got away from touristy zones and got to see something of everyday Dutch life.

The Netherlands is a nice country to visit, it is easy to get around and the population is very welcoming and friendly. Unfortunately the country's inscriptions on the World Heritage List and it's tentative sites don't pick out the highlights (Amsterdam and Reitveld Schroderhuis excluded).

Anyway, enjoy the trip

Don't worry!!! I am planning to visit also many other places recommended by my guidebook apart from the WHL and TL sites!!!

I was in the beemster this weekend, and although we are pretty negative about the polder as a WHS, it is spectacularly Dutch!

If you want indulge any obsession/addiction and go try and do so on a bicycle. If you can afford the time and energy a good route is to start in Amsterdam and cycle on the dike to Durgerdam, Volendam, Monnikedam and Edam then around the Schermer and Beemster and back to Amsterdam through De Rijp and Jisp and perhaps Zaanse Schans. You can even tick off a few forts, Spijkerboor is probably the best. This is quintessential Holland and amazingly rural so close to the capital. It is a long ride but this is the way to see Holland!

I will add that Beemster was the watermanagment site I liked the most. It certainly was not a must see, but I did like the atmosphere. And it was also a lesser spotted 'Double-site' due to the forts, and that is always good.

I was also struck by how rural the gaps in and around the Randstad felt. I wish it was that easy to get to countryside from London.

Of course if you do rent a bike and decide to miss a bit out or want to make up time the Dutch transport system is so good for taking bikes. Paul's suggestions took me back over 35 years when I did a similar trip by bike! But no WHS in those days!

I have to admit that I haven't visit any of these. Like meltwaterfalls said, these are really minor sites that I wouldn't construct a holiday around. I am half expecting the Netherlands to submit a complete new Tentative List in the coming year or so. The current list is very unsatisfying.

The Dutch part of the Wadden Sea will be up for nomination in 2009, and has a good chance of getting in I think. Visiting one of the Wadden islands is really worth it (especially those more to the east) but you do have to give it a couple of days.

It is true that it is unsatisfaying but I think that at least also the New Dutch Inundation Line is a good site, but i would see it rather as an extension to the Defence Line of Amsterdam.

why not go to see Van Nelle Factory in Rotterdam, not outstanding site but a very nice place to see dutch modernism.

The main fort at Muiden is the meeting point for the New Dutch Inundation line and the Defensive line so you can see both at the same time, wouldn't say it was anything particularly remarkable though. Muiden was a nice place to visit anyway, not stunning but nice.

I forgot about the Van Nelle Factory, it would be worth while oif you are interested in modernist architecture, could probably tie it in with a trip to Kinderdijk.

Historically the Stelling van Amsterdam is actually an extension to the Nieuwe Hollandse Waterlinie!

If you want to tick off both the Stelling van Amsterdam and the Nieuwe Hollandse Waterlinie in one go you can look at the forts at Pampus or Weesp. (Architecturally these forts belong to the later but were administered under the former).

Only a little further form Amsterdam is Naarden which is an impressive Vauban inspired walled city on the inundation line. Also visiting the forts near the "big rivers" or around Utrecht gives an interesting view on a different landscape to that in North Holland.

meltwaterfalls' suggestion of taking the watertaxi to Kinderdijk is a good one, but continue on to Dordrecht if you have time - this is another pretty medieval town.

Sorry for repeating meltwaterfalls I had not updated before posting.

Btw there is no fort at Muiden (it was never completed), there is a barracks which is part of both lines and Muiderslot a 13C castle.

I had to double check to make sure my memory was correct but there is fort in muiden along side the battery and the castle. The website is here if you wanted to have a look

if you are interested in "modern" architecture Dudok's works are worth looking for - Hilversum Town Hall in particular and (although you can't get in) the office block at Hoogovens IJmuiden