bit of a hike off the commuter rail, but there's a few decent hikes around Concord. Walden Pond area probably most notable among them

Middlesex Fells is accessible from the Malden stop on the Orange Line to the 132 bus (or biking that last bit instead of the bus).

Blue Hills will take a bit of time but is accessible from the Mattapan stop on the Red Line to the 716 bus. One of my favorite places in the area to hike though.

Middlesex Fells aren't far from Oak Grove.

Lincoln has 80 miles of trails

Breakheart Reservation entrance behind Wakefield High/NE Metro Tech is about a mile from Greenwood stop on the Haverill line. I don't think bikes are allowed off the paved paths other than at the powerlines

If you take the DownEaster up to Exeter, NH there's a nice river and lots of woods walks in town near Philips Academy. Very walkable little town. Also has kitschy shops and a couple nice breweries (Czar Brewing in particular is really good)

You probably want to follow this person's YouTube & posts here.

Put bike on T and go to Quincy Adams, then bike to Blue Hills. Not many great spots to lock up but if it’s a beater bike then don’t worry too much. Google shea memorial rink.

Lynn Woods is great if you don't mind taking a Lyft to/from the Lynn CR station

Also MilesPerHoward on Twitter. He's the guy that mapped the Urban Trail last year, and regularly posts about interesting hikes within the city (like hidden trails in Brookline!) Even as someone who's typically lazy AF, it's always interesting to learn about some of the lesser-known hikes in the area.

Orange line to oak Grove. Walk to pinnacle Rock trailhead. You're welcome

I love taking the 134 to the western cross fells trail head and hiking through to the eastern end. Then stroll over to Oak Grove, Orange line to North Station, and stop at Tasty Burger for lunch.

Take the commuter rail to Cohasset and you're right at Wompatuck State park.

There's also a pond and hiking area right by the Hanson stop.

Nobody has mentioned this yet so the commuter rail has a $10 weekend ticket so you could take the train both Saturday and Sunday for just $10.

Pine Banks Park has some short hiking trails, near Oak Grove Station in Malden.

If you take the orange line to Oak Grove there’s an entrance walking distance from the station

Take your bike on the commuter train to Fitchburg station. Leominster state forest, Crow hill and Wachusett mountain are all short rides away.

Red Line to Quincy Adams and then a bus can also get you to Blue Hills.

Prospect Hill Park in waltham.

You can access the bay circuit trail from the T