Currency
The euro. Spain is on the euro, so there is no separate national currency to convert in your head. What will catch you is dynamic currency conversion: card terminals in shops and restaurants, and airport ATMs in particular, will offer to bill you in Canadian dollars. The exchange rate on that offer is set by the terminal operator, not your bank, and it is always worse. Choose to be charged in euros every time.
Cards, cash and tipping
Contactless is accepted almost everywhere, including metro gates and EMT buses. Still carry some cash for older neighbourhood bars, market stalls and El Rastro. Tipping is not built into the culture the way it is in Toronto: service is included in the menu price, so you round up or leave loose change for good table service, and nothing at all at a bar counter. No percentage is expected and no one will chase you for one.
Power
Type C and Type F sockets — two round pins, with Type F adding earth clips on the sides — running at 230 volts, 50 Hz. Anything marked 100-240V (phone bricks, laptop chargers, most modern cameras) needs only a cheap plug adapter. Anything 120-volt-only with a heating element — some hair straighteners, curling irons, small travel kettles — needs a real voltage converter or it will burn out on the first use.
Tap water
Safe and genuinely good. Madrid's supply comes off the Sierra de Guadarrama and locals drink it without a second thought. Restaurants will default to bottled, so ask for agua del grifo. Public fountains around Retiro and the other parks are potable unless a sign says otherwise.
Language
Castilian Spanish. English is comfortable in museums, hotels and central restaurants but drops off quickly in neighbourhood bars, markets and with taxi drivers, and menus in the old quarters are often Spanish-only. A handful of words goes a disproportionately long way here.
Watch out for
Pickpocketing, not violence — Madrid is a safe city to walk at night. Canada's own travel advice names Madrid-Barajas airport, Atocha station, Gran Vía, Plaza Mayor and the surrounding streets, and Retiro park as the places to be careful. The method is distraction: someone asking directions, pointing out a stain on your jacket, or a sudden scrum at a metro door. Separately, the same advice warns of people posing as plainclothes police and asking to see your passport, ID or wallet — ask to see an official badge and do not hand over documents or cash.