× The city was very wonderful.
√ The city was (absolutely/really) wonderful.
Wonderful is a non-gradable adjective. This means that the adjective is at the top of its scale: wonderful means ‘extremely nice or good’ or ‘at the top of the scale of nice/good’. There are many non-gradable adjectives:
cold: freezing
hot: boiling
good: spectacular/ wonderful, etc.
bad: awful/ terrible, etc.
Non-gradable adjectives can not be preceded by very, they should be preceded by really or absolutely: ‘The book was really terrible.’ ‘She is absolutely brilliant.’