An idea for the city of Rotterdam
With the already in place infrastructure, you can travel a complete loop around the river Maas.
1. Take metro line D or E from the north, heading south towards the river.
2. Pass underneath the river and alight at Wilhelminaplein station.
3. Transfer to the over ground platform and take tram 23 or 25 back over the river on the Erasmus bridge.
4. Alight at Leuvehaven station and return underground for the metro to re-join the original path crossing underneath the river once more.
The looping can be carried out in both directions.
Illustration by Maaike Canne