Hop on Hop off is a smart ship tour, if your port stop is at least 3-4 hours long. I'm a senior (70 in a few weeks) traveled with 3 other seniors on a TA from Miami to Barcelona April 2022 (Regent Splendor), and spent 4 days there. We all read "The Shadow of The Wind " by Carlos Ruiz Zafón, which has "a walk in the footsteps" walking tour of Barcelona at the end of the book, which was set in Barcelona in the 20th century (historical/fiction/mystery/murders/a little fantasy, books, restaurants, bookshops, libraries, Gothic area, Las Ramblas, beaches near the port). Many of the important places in the book (a series of books actually) are real places you can visit or pass by (wave at) on the hop-on-hop-off. There are 2 different hop on-hop off bus tours and each lasts about 2 hours, if you stay on for the full circle. You can hop on a red or green tour from the Port of Barcelona. We did both on one afternoon, not worried about a cruise departing, tho. It was raining, and we were so happy not to hop off!. Had great tapas, great meals on streets and restaurants mentioned in the book (which we also visited 3 years ago, before we read the book). We spent 4 nights same hotel on Las Ramblas as our 2019 visit, on a 6 week land trip through Morocco, Barcelona, Lisbon, Paris, London, Oxford, Brecon Wales, NYC). I would return to Barcelona in a heartbeat, and loved walking Las Ramblas alone day or night, no problemo! Happy to offer names of restaurants if requested. The book is a really fun quick read, even if you are not traveling there. 🙂