This place gives a stunning view on what happens when the Ocean and rocks come together . Impressive little stop whilst walking alongside the path near to the sea

Very typical place in Cascais were you can buy souvenirs and see the Atlantic Ocean in a geological formation thar resembles a mouth. When the sea is very rough the sound produced by the water entering the cave sounds spetacular resembling a roar and that's why people call it mouth of hell (Boca do Inferno)

I had high hopes for an amazing place given some reviews. First - it's more than a 20 minute walk from downtown Cascais like the tour books say. I'd say about 30 minutes if walking briskly and not stopping to enjoy the scenery. The signage isn't 100% clear for pedestrians. But it is a lovely ocean front walk - mostly gentle uphill on the way. The inferno cliff itself is pretty, but I think it depends on what you're used to. Coming from California, I guess I'm spoiled and can see beautiful spots like this any time. There were no wild ocean sprays akin to an inferno. I'd say it's not worth a special trip for this unless you have plenty of time to go slow and enjoy some pretty (but not rare) scenery. Downtown Cascais has some bicycles you can rent which would be pleasant.