Large diamond factory in the centre of Amsterdam. You can get free tours here, and of course buy diamonds and other jewellery.

The diamond cuttery has existed since 1945.

The factory offers free tours, in several languages. You can book that online, or just go there and wait for the next available tour.

Since April 2015, they have a shop at P.C. Hooftstraat 84 (this is the main luxury shopping street of Amsterdam).

Address:
Nieuwe Uilenburgerstraat 173-175, Amsterdam
Web:
http://www.gassan.com/

Opening hours:
Gassan is open 365 days per year, from 9-5 (on some holidays it may open a little later)