The OT in Alençon is in a fine old building, La maison d'Ozé, and has a small heritage orchard next door. The stretch of the river nearby is pleasant and walkable. The center of town has some great old buildings. There's the lace museum and the childhood home of St Therese (both recommended to us but we've never been). The post office facade is classic PTT. The Halle au Ble was called the hoop skirt when it was built (it's round). I can heartily recommend the boulangerie/patisserie across from it. First Saturday of every month on the pavements surrounding the Halle au Blé there is a flea market. Supposedly the stained glass in the basilica is among the finest in Europe, and on a sunny day it may well be but I guess we've been unlucky in our timing. Would you be interested in the departemental archives? It looks like there are markets on Tues, Thurs, Sat, and Sun mornings. I think there's a capoeira club in Alençon. I've read that the Chateau des Ducs is open but can't confirm it. There's supposedly a new park there named for Simone Veil.
Here's a list of parks:
We've been to Alençon on a Saturday when the streets and shops were full and lively, and also on a Monday when the shopping part of downtown was lifeless and slightly depressing.
If you can get to Carrouges, it's worth the trip. It's an all-brick chateau around a courtyard, surrounded by a moat, with a brick gatehouse. Next door is the HQ of the Parc Naturel Regional de Normandie-Maine.
I've seen you posting about Nogent le Rotrou and that interests me because that's our favorite Saturday market when we're in the Perche. I'd love to hear more from you about Nogent.
Enjoy your trip to Alençon.