Toronto

===Topography===
{{further|Toronto ravine system}}
{{More citations needed section|date=July 2016}}
[[File:Leaside Bridge 2023.jpg|thumb|[[Leaside Bridge]] crossing the [[Don River (Ontario)|Don valley ravine]]. The [[Toronto ravine system]] and its [[Toronto waterway system|waterways]] cut through the city's landscape.]]
The city is mostly flat or gentle hills, and the land gently slopes upward away from the lake. The flat land is interrupted by the [[Toronto ravine system]], which is cut by numerous creeks and rivers of the [[Toronto waterway system]], most notably the Humber River in the west end, the [[Don River (Ontario)|Don River]] east of downtown (these two rivers flanking and defining the Toronto Harbour), and the Rouge River at the city's eastern limits. Most of the ravines and valley lands in Toronto today are parklands and recreational trails are laid out along the ravines and valleys. The original town was laid out in a [[grid plan]] on the flat plain north of the harbour, and this plan was extended outwards as the city grew. The width and depth of several of the ravines and valleys are such that several grid streets, such as [[Finch Avenue]], [[Leslie Street]], [[Lawrence Avenue]], and [[St. Clair Avenue]], terminate on one side of a ravine or valley and continue on the other side. Toronto has many bridges spanning the ravines. Large bridges such as the [[Prince Edward Viaduct]] were built to span broad river valleys.

Despite its deep ravines, Toronto is not remarkably hilly, but its elevation does increase steadily away from the lake. Elevation differences range from {{convert|76.5|m|ft|0|abbr=}} [[Above mean sea level|above sea level]] at the Lake Ontario shore to {{convert|209|m|ft|0|abbr=on}} above sea level near the [[York University]] grounds in the city's north end at the intersection of [[Keele Street]] and Steeles Avenue.<ref>{{cite web|url=https://www.toronto.ca/city-government/data-research-maps/toronto-at-a-glance/|title=City of Toronto: Toronto at a Glance, Geography|website=Toronto.ca|date=November 14, 2017|publisher=City of Toronto|access-date=March 7, 2019|archive-url=https://web.archive.org/web/20180425115350/https://www.toronto.ca/city-government/data-research-maps/toronto-at-a-glance/|archive-date=April 25, 2018|url-status=live}}</ref> There are occasional hilly areas; in particular, [[Midtown, Toronto|midtown Toronto]] has several sharply sloping hills. Lake Ontario remains occasionally visible from the peaks of these ridges as far north as Eglinton Avenue, {{convert|7|to|8|km|mi}} inland.
[[File:Topographical Map of Toronto.png|thumb|left|upright=1.2|Topographical map of Toronto. The terrain increases steadily away from the shoreline.]]
The other major geographical feature of Toronto is its escarpments. During the [[Last Glacial Period|last ice age]], the lower part of Toronto was beneath [[Glacial Lake Iroquois]]. Today, a series of [[escarpment]]s mark the lake's former boundary, known as the "Iroquois Shoreline". The escarpments are most prominent from [[Victoria Park Avenue]] to the mouth of [[Highland Creek (Toronto)|Highland Creek]], where they form the [[Scarborough Bluffs]]. Other observable sections include the area near St. Clair Avenue West between [[Bathurst Street (Toronto)|Bathurst Street]] and the Don River, and north of [[Davenport Road]] from Caledonia to [[Spadina Avenue|Spadina Road]]; the [[Casa Loma]] grounds sit above this escarpment.<ref>{{Cite web|url=https://www.blogto.com/city/2012/07/a_brief_history_of_the_lake_iroquois_shoreline_in_toronto/|title=A brief history of the Lake Iroquois shoreline in Toronto|website=www.blogto.com|language=en|access-date=April 28, 2020|archive-date=April 14, 2020|archive-url=https://web.archive.org/web/20200414000450/https://www.blogto.com/city/2012/07/a_brief_history_of_the_lake_iroquois_shoreline_in_toronto/|url-status=live}}</ref>

The geography of the lakeshore has dramatically changed since the first settlement of Toronto. Much of the land on the harbour's north shore is landfill, filled in during the late 19th century. Until then, the lakefront docks (then known as wharves) were set back farther inland than today. Much of the adjacent Port Lands on the harbour's east side was a [[wetland]] filled in early in the 20th century.<ref name="utoronto1">{{cite web |url=http://maps.library.utoronto.ca/dvhmp/ashbridges-bay.html |title=Don River Valley Historical Mapping Project |publisher=Maps.library.utoronto.ca |access-date=July 14, 2016 |archive-date=May 24, 2016 |archive-url=https://web.archive.org/web/20160524162113/http://maps.library.utoronto.ca/dvhmp/ashbridges-bay.html |url-status=live }}</ref> The shoreline from the harbour west to the Humber River has been extended into the lake. Further west, landfill has been used to create extensions of land such as Humber Bay Park.
[[File:Views from the CN Tower Laslovarga (20).JPG|thumb|View of the [[Toronto Islands]], an island chain that bounds [[Toronto Harbour#Inner Harbour|Toronto's Inner Harbour]]]]
The Toronto Islands were a natural peninsula until a storm in 1858 severed their connection to the mainland,<ref>{{Cite news|url=https://nowtoronto.com/news/tempestuous-isle/|title=Tempestuous isle: A tragic history of Toronto Islands|last=Longley|first=Richard|date=September 14, 2017|work=NOW Magazine|access-date=February 14, 2018|language=en-us|archive-url=https://web.archive.org/web/20180215084610/https://nowtoronto.com/news/tempestuous-isle/|archive-date=February 15, 2018|url-status=dead}}</ref> creating a channel to the harbour. The peninsula was formed by [[longshore drift]] taking the sediments deposited along the Scarborough Bluffs shore and transporting them to the Islands area.

The other source of sediment for the Port Lands wetland and the peninsula was the deposition of the Don River, which carved a wide valley through the sedimentary land of Toronto and deposited it in the shallow harbour. The harbour and the channel of the Don River have been dredged numerous times for shipping. The lower section of the Don River was straightened and channelled in the 19th century. The former mouth drained into a wetland; today, the Don River drains into the harbour through a concrete waterway, the [[Keating Channel]]. To mitigate flooding in the area, as well as to create parkland, a second more natural mouth is being built to the south during the first half of the 2020s, thereby creating [[Villiers Island]].