Everybody in Toronto knows about Sir Henry Pellatt?s medieval-style castle in the middle of downtown. But if you haven?t visited Casa Loma, you might not be aware that the estate includes long (and chilly) underground tunnels leading to Walmer Road, the site of the eccentric millionaire?s stables, carriage rooms and potting shed.

This weekend, Casa Loma invites the public, free of charge, to visit this lesser-known part of Sir Henry?s legacy during Doors Open Toronto. (Visitors must still pay full admission to enter the castle.)

From 10 a.m. to 3 p.m., visitors can view the mahogany stalls where Pellatt kept his numerous pedigree horses, including favourites such as Matchless, The Widow and Prince Highgate. They can also view the wide variety of plants on display in the potting shed ? and even get an archery lesson.

?The stables and potting shed, as well as the carriage rooms, were built around 1906 ? before the castle itself,? says Natasha Santos, an employee with Casa Loma. ?It?s very extravagant.?

This section of the estate also includes Pellatt?s original furnace room. ?He had a furnace room, plumbing, heating and electricity,? Santos explains. ?He had about fifty-two phones and his own switchboard operator in the house. So he was really ahead of his time… He brought electricity to Toronto ? he actually built the dam in Niagara Falls.

?There are also underground tunnels that lead to other places in Toronto,? she adds.