Peel Cathedral — officially the Cathedral Church of Saint German — is a modest but dignified Gothic Revival building in the town centre, a short walk from the harbour. It replaced an earlier structure on St Patrick's Isle and was built in stages during the 19th and 20th centuries. The interior is quietly pleasing: good stone work, decent stained glass, and a sense of space that belies the modest exterior.
The cathedral is open to visitors most days. It's a working cathedral rather than a tourist attraction, so the atmosphere is peaceful and services are held regularly. The building won't detain you long, but if you're in Peel for the day it's worth ten minutes to see the interior.