I agree, it’d be great to have an app you could navigate after the trip 
In the meantime you’ve got a couple of options…
You could try searching your transactions by location.
Or if you’re feeling adventurous (& nerdy) you could try out @walking_fishy’s awesome Mondo Dashboard, which displays a map of your transactions with the merchant name & purchase amount, when you click on each pin.
To do that, just set up a non-confidential client key in the Monzo developer’s API playground.
The only caveat is that the app only lists your first 100 transactions (rather than 100 most recent, which was the intended design) so if you’ve been a Monzo user for a while, it might not have the transactions from your holiday 