Same with tradeshows: I have many times been on tradeshows on buildup days. It is a huge mess, full of crates and packaging. Next day, everything is glorious and neat. Just for 3-4 days of 'show'
Also similar: Join a local Toastmasters group. This is a global organization where you learn and practice to speak in front of a group, both prepared speeches and spontaneous. It may find weird to join it, but I would advice to visit one once in your neighborhood: They are all super friendly and I have seen dozens of people come in and move from shy and awkward to great storytellers in just a year or so.
I live in The Netherlands (actually in the same city as the photo's were taken): There is a very large difference in traffic density and complexity between the larger cities such as Amsterdam, Rotterdam, The Hague, Utrecht and the rest of the country (including middle sized cities).
When I visit one of those larger cities, I am also constantly looking for bikes everywhere not to be crashing into me.
Also fun debugging VoIP traffic to the local network, and seeing dns-queries from collegues PCs on the network, then asking them: Are you visiting xyz-webpage, and seeing their reaction!?
Such a great tool and 100% free. Use it often to debug network issues and see where devices connect to. Like someone else said: a multimeter for networks.
Also used it to learn about WiFi connection setup with acces point. Can see all the beacon packets and WiFi packets
I was a very early adopter of Ethereal. My team had a Sniffer PC, but either it was being used by someone else or it didn't adequately decode protocols.