End of december 2024 I visited 2 of the plantations. I also passed by one other.

Landhuis Ascension: gate was closed; I could only see from the street. Website tells it is reserved for the Dutch Marine. Just next to the Landhuis you have Kas di pal'i maishi - Kunuku House. It is just at the street. This one is a little house with a roof from Mais.

Landhuis Savonet: very close to the road to Westpunt and it has its own busstop. There is a small museum in the building. Nothing special, but you can enter the building. Price was only 5 USD. The landhuis is also the ticket counter from the Christoffel National Park.

https://www.christoffelpark.org/nl_NL

Landhuis Knip: The house is at one side of the road; on the other side of the street you also have some buildings. There is also a museum. I think there is a guided tour for 25 USD, but i had not much time to check, otherwise I would miss the last bus. Website tells 15 USD for ticket.

https://fundashonmuseotula.com/