Here's a picture of what turns out to be the finishing tower at the Bosbaan in Amsterdamse Bos. It was demolished when the Bosbaan was widened to meet international rowing competition requirements. I can't tell, though, if this was the same as the "tribune building" "from the twenties" [??] that Korteknie Stuhlmacher Architects mention was also demolished in order that they could build a new boathouse for Okeanos, the student rowing association, and RKNB, the Royal Dutch Rowing Association.
There's also a new finish tower, but it's not really a tower, just a box.
Roeigebouw Amstelveen, 2000, 2005 | Korteknie Stuhlmacher Architecten [kortekniestuhlmacher.nl]
