Start off your visit on the 27th (Wed): pause for some serene contemplation at Rock Church, brush up on your military savvy at Sea Fortress Suomenlinna, contemplate in the serene atmosphere at Uspenskin Cathedral (Uspenskin Katedraali), then don't miss a visit to Senate Square, and finally take in the architecture and atmosphere at Helsinki Cathedral.
To find where to stay, other places to visit, reviews, and tourist information, read Helsinki day trip planning site .
If you are flying in from Mexico, the closest major airport is Helsinki Vantaa Airport. In March, plan for daily highs up to 3°C, and evening lows to -5°C. Finish up your sightseeing early on the 27th (Wed) so you can travel back home.