Cornwall (Marazion) Routes

I was in Falmouth a couple of years ago and did some great cycling around the Lizard. The only downside was that the locals didn't care for cyclists much; lots of close passes and someone even said he'd knock me off next time as I tried to make a turn off a road. All a bit 'get orf my laand' for me!

Agree that the ride from St Just to St Ives along the Atlantic Highway is fantastic, particularly with a strong-westerly, less so with a headwind! Worth rolling down the hill to Cape Cornwall from St Just rather than Land's End, if not the climb back up. Follow rapid4's suggestion, do it clockwise and take the minor roads from Hayle down through St Erth back to Marazion to get you back in 3 hours.

You should be able to get in Marazion- Lelant- St Ives- Zennor- Lands End- Mousehole/ Penzance - and back to Marazion, i.e. the whole of West Cornwall.
Check out this for inspiration https://www.strava.com/activities/203497209 I admit that's 3hr 45 but on that sportive route they took you up to Camborne area before hitting the north coast- if you follow your nose over to Lelant instead you'll be spot on for time.
TBH that A30 between where you are and Lelant isn't tooo bad, it's all single carriageway and is quite slow (for a trunk road).

So long as you don't spend too long slogging along the A30, the area is ripe with beautiful routes. The primary recommendation would be to hear North-West and admire the swooping North Coast running roughly from Zennor to St. Just, although you could throw in St. Ives if you want another point of interest (though personally, I think St. Ives is large and interesting enough to warrant a more thorough visit on foot).

Zennor itself is small, gorgeous, and perfect for throwing into a bike ride ride as the whole village is about one road wide. The pub is a bit pricey, but the village might be a nice place to stop, have something out of a back pocket and admire the view.

Further down the coast is Pendeen, which isn't quite as picturesque, but does boast an excellent, well priced coffee shop called Heather's, which offers an eclectic array of cakes and magical jacket potatoes. And good coffee.

This would probably be a good point to turn inland - unless you want to visit Cape Cornwall or Land's End - as you're plunged immediately into the lush fields, hedgerows, hills, and wild country that characterise the region. You can either head back home, or if feeling like something more maritime, cross coast to coast to the fishing villages of Mousehole and Newlyn. Mousehole particularly is as cute as a button.

Newly quickly becomes Penzance, but Penzance to Marazion is a bit awkward due to the A30. However, there is a shared path, which I I'd hesitantly recommend despite its flaws, as the views are so good. It might be a nice point to trundle along in a light gear and reflect on your own mini Coast to Coast as the sun sets (or doesn't). The North and South Coasts certainly provide a lot to think about and compare.

just be careful of those high side stonewalled lanes, with the wind coming off the coast I had real problems hearing or seeing oncoming traffic. There's lots of it down there even on the tiny lanes. Beautiful riding country though, especially if you like rock hard, shorty, punchy climbs..