honeymoon in Lisbon and Porto, looking for unique activities

I will be having my honeymoon in Portugal at the end of this month with home bases in Lisbon and Porto. I'm just looking for unique reputable activities to spice up the trip. Ex: romantic boat ride down scenic river or sea, helicopter ride, unique wine tours for two, sunset spots, restaurant tasting package etc.

I would love to hear from people who've done something similar to the list above in Lisbon or Porto. Any suggestions or advice would help.

Thanks!