Full Day Trips from Santiago

I will be in Santiago for 2 days (including a full day) in total and would like some advice on day trips from Santiago. I am going to be there on the 22nd of March and was planning this day trip for the 23rd. All advice is welcome. And if there are other pilgrims who may have the day free and would like some company in exploring, please do contact me.

thanks

Thank you for the ideas. I will actually have (in addition to the full day), 2 half days (after 2pm one day and up to 4pm the third day), so I think I will get a chance to explore Santiago for sure. I was thinking of taking a taxi to Finisterre on the afternoon of the 30th when I reach Santiago after the trip to complete the trip in sequence. Muxia however sounds interesting - there are buses leaving at 8:45 from Santiago and returning back at 2:30pm, so that may be a good option with the right amount of time there (2-3 hours) to explore.

The one option I was thinking of which may be a stretch is to take the train to Madrid at 5am, reaching at 10am, spending a few hours and taking the train back either the next morning or late that night. But I am not sure of this.