Most tourists only talk about the Jerónimos Monastery. They've probably seen the fantastic pictures of the cloisters and now understandably want to have one of those too. It was the same for me, but the crowds were so big that I spontaneously went to the monastery church (Church of St. María of Belém), and what can I say - it's worth the trip. I can't understand why there hasn't been a highlight for this yet?
What makes this trip so worth seeing:
1. Admission to the church is free.
2. There are countless (photo) opportunities waiting to be discovered.
3. Vasco da Gama's tomb is in the transept.
4. And with the money you save, you can treat yourself to some natas 😋 (My recommendation - Manteigaria Fabricia de Pasteis de Nata. It's just a few steps away).
By the way, the entrance to the church is the same "entrance area" as to the monastery. The entrance to both attractions is at the west portal (standing on the main street, facing the two buildings, approximately in the middle). To the left is the entrance to the monastery, and to the right is the entrance to the church. Make sure you queue properly. My tip: go there about half an hour to three-quarters of an hour before mass. Then you won't have the entire church to see, but there will be far fewer people around you who want to take the exact same photo as you 😉🙂.
Mosteiro dos Jerónimos - Admission is €14. Tickets can be purchased online or on-site (directly opposite the monastery entrance and it's also signposted).
Santa Maria de Belém - I found an online posting that shorts and skirts are not permitted. I was allowed in wearing shorts that went above the knee.