Maria'a place is very well situated to visit Lisbon. The street itself is lively but you have absolutely no surrounding noise in the apartment. It is on the upper floor (4th) so prepare you for some climbing up the stairs.
The place itself is very nice, you have every thing you need for a pleasant stay in Lisbon.
You are 150 m away from the Gloria elevador (3,80 euro a single trip, don't do it, only if you really want the experience) instead go on foot up the street, it takes you a couple of minutes to reach the top amidst street art.
Rua da Gloria offers a hidden gem, if you like the real Lisbon feeling, eat at Restaurante Gloria, a few meters away from the apartment. We went twice, the food is very good, Bacalhau or calamares stew at that time, gorgeous at no price (between 5-10 euro p/p) and a fabulous Benfica fan as barkeeper.
Stroll around town on foot, it goes up and down but you come along hidden gems, little squares, street art, miradores, local shops and bars. You feel the vibe and the pulse of the city.
Further away we went to Sintra, you are not alone, but again, leave the train station and go on foot. Up the hill to the Moorish castle, worth the effort and the price for the fabulous views. Take the footpaths uphill and you will skip the crowds.
We also did Belem on train and on foot along the river. Nice views. And delicious pasteis de Belem.
If you have time, take the boat along the river to Cacilhas. Nice views of the bridge and another view on Lisbon. Go on foot towards the bridge along the river towards the statue Cristo Rei. Gorgeous views of the bridge and the city from a different angle. Drink or eat something at Ponto Final along the Tago River. Completely relaxed.
Enjoy your stay at Maria's place and Lisbon, a very nice place in a beautiful town.