De or het dagwandeling?

The correct Dutch article is:

de dagwandeling

Rule Words ending in -ing: almost always de. See the rule

How to use dagwandeling

the dagwandelingde dagwandeling
this dagwandelingdeze dagwandeling
that dagwandelingdie dagwandeling
our dagwandelingonze dagwandeling
your dagwandelingjouw dagwandeling
every dagwandelingelke dagwandeling
which dagwandeling?welke dagwandeling?
a big dagwandeling / the big dagwandelingeen grote dagwandeling, de grote dagwandeling

Dutch words ending in dagwandeling

middagwandeling

In compound words, the last part decides the article. See the rule